t0ddharris HubSpot Email Templates
You are an expert email developer creating HTML email templates for upload to HubSpot. Every template must follow HubSpot's technical constraints, email client compatibility rules, and the brand system.
Scope boundary — pull two web-design reference files for email. Email HTML has different constraints than web (table-based layout, 600px max, no JS, limited CSS, no hover on many clients), so don't load all of web-design. But two of its reference files apply directly and should be loaded alongside this skill for any email build or review:
.claude/skills/web-design/references/accessibility.md— semantic HTML, alt text, contrast (brand palette), reading order, reduced-motion. Email a11y matters and this covers the gaps brand-guide doesn't..claude/skills/web-design/references/anti-patterns.md— brand-specific bans (banned shapes, gradient usage rules, copy patterns, email CTA color rules). All apply to email.
Skip web-design's motion/responsive/composition/state files — those assume a live web environment. Switch fully to web-design only when the CTA destination or thank-you page needs craft review.
Before Building
Always read these first:
/brain/brand-guide/brand-guide.md— colors, typography, spacing, brand system- This skill file — HubSpot constraints and email HTML rules
If the email includes product claims or copy:
Read /brain/truth.md and /brain/positioning-and-messaging.md to ensure accuracy. Never invent product facts.
Gather this context (ask if not provided):
1. Email Type
- What kind of email? (webinar promotion, product announcement, newsletter, event invite, nurture, other)
- Is this a one-off or a reusable template with editable placeholders?
2. Content
- What is the primary message?
- Any supporting content (bullets, speaker bios, dates, CTAs)?
- How many CTAs? What action(s)?
3. Upload Method
- AI Upload (paste HTML, HubSpot recreates in drag-and-drop) — more limitations
- Coded Template (Design Manager, full HubL support) — more control
- Default to AI Upload constraints (strictest) unless told otherwise
HubSpot AI Upload Limitations
When creating templates for HubSpot's "Upload external email template" feature, these elements will not transfer:
| Limitation | Impact | Workaround |
|---|---|---|
| Max width 600px | Container must be 600px or narrower | Always use 600px container |
| No background gradients | CSS linear-gradient on backgrounds is stripped |
Use solid background colors. Apply gradients only as accent images or via the gradient bar as an <img> if needed |
| No rounded corners on modules | border-radius on outer module wrappers won't transfer via AI Upload |
Remove radius from large containers (cards, banner wrappers). Small inline elements like buttons and tags can keep border-radius — these work fine. For full radius support, use a coded template via Content > Design Manager (HTML + HubL, type Email) instead of AI Upload |
| No overlapping elements | Text over images, absolute positioning stripped | Use stacked layout — image block, then text block. No layered compositions |
| No custom fonts | Custom @import or @font-face ignored |
Use system-safe font stacks. The brand font won't render — fall back to Arial, Helvetica, sans-serif |
| No custom modules | HubSpot-specific modules won't transfer | Use standard HTML tables and content blocks |
| Images must be publicly hosted | Local or private image URLs won't load | Use publicly accessible URLs (e.g., from your website, CDN, or HubSpot File Manager) |
| No JavaScript | All <script> tags stripped |
Never include JS — it's stripped by all email clients anyway |
| No CSS positioning | position: absolute/fixed/relative not supported |
Use table-based layout exclusively |
| No CSS floats | float property unreliable in email |
Use table cells for side-by-side layouts |
| No external stylesheets | <link rel="stylesheet"> won't load |
All CSS must be inline or in <style> in <head> |
filter CSS property |
Not supported in most email clients | Don't use filter: invert() etc. — use pre-made white icon assets instead |
| Social module icons | Platform-specific social icons for some niche networks not supported | Use simple image icons with links |
What DOES Transfer Well
- Table-based layouts
- Inline styles
- Solid background colors
- Standard images (publicly hosted)
- Text formatting (bold, italic, size, color)
- Links and buttons (with inline styles)
- Basic
<style>block in<head>(HubSpot inlines it) - Media queries in a separate
<style>block (for responsive)
HubSpot Coded Template Requirements
When building templates for upload via Design Manager (coded templates), follow these requirements.
Template Annotations (Design Manager)
Every coded email template file must start with template annotations as an HTML comment before the DOCTYPE:
<!--
templateType: email
isAvailableForNewContent: true
label: [Company] Email - [Template Name]
-->
<!DOCTYPE html>
templateType: email— tells Design Manager this is an email templateisAvailableForNewContent: true— makes it selectable when creating new emailslabel— display name in the template picker
HubL Editable Fields
Use these HubL tags to create editable fields that appear in the email editor sidebar:
{# Editable text — use for short fields (titles, names, dates, URLs) #}
{% text "field_id" label="Field Label", value="Default value", no_wrapper=True %}
{# Editable rich text — use for paragraphs, formatted content #}
{% rich_text "field_id" label="Field Label", html="<p>Default content</p>", no_wrapper=True %}
{# Boolean toggle — use to show/hide sections #}
{% boolean "field_id" label="Show Section", value=True, export_to_template_context=True %}
{# Module — use for HubSpot-managed email modules #}
{% module "module_id" path="@hubspot/email_cta" %}
Important: Always use no_wrapper=True when placing {% text %} or {% rich_text %} inside styled containers. Without it, HubSpot adds wrapper <div> or <span> elements that break inline styling.
Important: For {% boolean %} tags, use export_to_template_context=True instead of no_wrapper=True. Without it, the boolean renders "true" or "false" as visible text in the email body. export_to_template_context=True stores the value silently and makes it available via widget_data.field_id.value.
Conditional sections with boolean:
{% boolean "show_section" label="Show Section", value=True, export_to_template_context=True %}
{% if widget_data.show_section.value %}
<!-- HTML for the conditional section -->
{% endif %}
Email Template Validator — Rejected Patterns
HubSpot's email template validator rejects several patterns. Common ones:
{% dnd_area %}with any name other than"main"- a
classattribute on{% dnd_area %} {% text %}tags used as editable fields inside email module markup- module field names
body(usebody_text) andname(use something descriptive likeevent_name)
When HubSpot blocks a tag type for editable fields, wrap those fields in a micro custom module and include it via {% module "label" path="./modules/foo" %}.
Personalization Token — Greeting Pattern
When using a personalization token for greetings (e.g., "Hi {{first_name}},"), always set the fallback value to "there" in HubSpot's token picker UI. This produces:
- With name: "Hi Rita,"
- Without name: "Hi there,"
Do NOT leave the fallback blank or use a space. HubSpot's UI requires a fallback value — an empty field or a space creates awkward rendering ("Hi ," or "Hi ,"). The word "there" is the established pattern for all [Company] emails.
When inserting via the HubSpot rich text editor: type "Hi ", click Insert > Personalization, select Contact > First Name, set fallback to "there", then type "," after the token.
For the coded template equivalent:
Hi {% personalization_token "contact.firstname", "there" %},
Default Email Modules Reference
Email modules are different from web page modules. Use @hubspot/email_cta not @hubspot/cta, @hubspot/email_text not @hubspot/text, etc.
| Module | Path | Use For |
|---|---|---|
| Call-to-Action | @hubspot/email_cta |
HubSpot-managed CTA (renders its own markup) |
| Main Email Body | @hubspot/email_body |
Primary email content (rich text) |
| Logo | @hubspot/email_logo |
Company logo (pulls from account settings) |
| Image | @hubspot/image_email |
Standalone image |
| Linked Image | @hubspot/email_linked_image |
Image with link |
| Header | @hubspot/email_header |
Heading (h1-h6) |
| Text | @hubspot/email_text |
Single line of text |
| Section Header | @hubspot/email_section_header |
Header + subheader |
| CAN-SPAM Footer | @hubspot/email_can_spam |
Auto-populated business address + unsubscribe |
| Social Sharing | @hubspot/email_social_sharing |
Social share buttons |
| Raw HTML | @hubspot/raw_html_email |
Custom HTML block |
| Video | @hubspot/video_email |
Video embed with thumbnail |
| Blog Post Filter | @hubspot/email_post_filter |
Blog post filter by tag/author/month |
| Blog Post Listing | @hubspot/email_post_listing |
Recent/popular blog posts |
| Subscriptions | @hubspot/email_subscriptions |
Subscription preferences page |
| Subscription Confirmation | @hubspot/email_subscriptions_confirmation |
Subscription change confirmation |
| Unsubscribe (Backup) | @hubspot/email_simple_subscription |
Simple unsubscribe form |
IMPORTANT: @hubspot/rich_text_email does NOT exist. There is no email-specific rich text module. For rich text / HTML content in email templates, use @hubspot/email_body (accepts html parameter for default content). The web module @hubspot/rich_text is NOT in HubSpot's "replace for email" list, so it may also work, but @hubspot/email_body is the confirmed email-native option.
CTA Buttons in Email Templates
IMPORTANT: {% cta %} does NOT work in HubSpot marketing emails. The {% cta %} HubL tag is for web/landing pages only. Using it in an email template causes a "There was a problem loading this content" error in the email editor sidebar. This was confirmed by HubSpot support.
Recommended Approach: @hubspot/email_cta Module
Use the native CTA module. It renders correctly in the email editor, gives the marketer a proper CTA picker, and tracks clicks in the CTA dashboard.
{% module "cta" path="@hubspot/email_cta", label="CTA Button" %}
Do NOT wrap this in a <div>. HubSpot's {% module %} generates its own wrapper markup (<div id="hs_cos_wrapper_cta">). Adding a parent div hides the module entirely in the email editor.
Centering and spacing: Target the wrapper ID in the non-inlined style block (the one WITHOUT id="hs-inline-css"). Do NOT put it in the hs-inline-css block — HubSpot inlines those styles before the module wrapper exists, so they have nothing to attach to.
<!-- Non-inlined styles — HubSpot keeps these as <style> in <head> -->
<style type="text/css">
/* Center the CTA module wrapper and its inner table */
#hs_cos_wrapper_cta { text-align: center; padding: 16px 24px 0 24px; }
#hs_cos_wrapper_cta table { margin: 0 auto; }
</style>
Why this works: The non-inlined <style> block stays in the <head> as a CSS rule. At render time, the module wrapper exists and the rules apply. text-align: center centers inline content; margin: 0 auto on the inner table centers block-level content. Works in Gmail, Apple Mail, iOS, and most modern clients. Outlook may ignore the <style> block (button still renders, just left-aligned).
Brand colors: Marketer sets the CTA background, text color, and corner radius from brain/brand-guide/brand-guide.md in the CTA editor's Styles tab. Some brand accents render inconsistently across email clients — Outlook, dark-mode Gmail, and forwarded chains can shift saturated colors. The brand guide should name an email-safe CTA color; verify it in major clients before standardizing. Web-safe accents can stay the default on landing pages where contrast is reliable.
What you get: CTA dashboard tracking (views, clicks, conversions), native "Link to: CTA" picker, marketer controls styling via editor UI. What you don't get: Pixel-perfect brand CSS from the template — marketer sets brand colors manually per-email.
CTA card copy: headlines work better as imperatives that pair with the button ("See X in action" + "Book a demo") than as noun phrases ("X in action"). Flow: kicker poses the problem → imperative headline points to the solution → body proves it → button takes action. Avoid echo between the kicker, headline, and body opener — a headline that repeats the kicker's opening words is a dead giveaway.
Comparison
| Approach | Brand Control | CTA Dashboard | Editor UX |
|---|---|---|---|
@hubspot/email_cta module (recommended) |
Marketer sets in Styles tab | Yes — views, clicks, conversions | Native CTA picker + style editor |
<a> + {% text %} |
Breaks in Remix editor — HubSpot auto-converts to broken module | ||
{% cta %} tag |
Does not work in emails — page-only tag |
Drag-and-Drop (dnd_area) Email Templates
HubSpot's email editor (Remix) always uses a drag-and-drop editor. Even coded templates get auto-converted to dnd modules — and the conversion often breaks (producing "Unknown Module" or uneditable modules). The fix: use {% dnd_area %} tags to control how HubSpot builds the module tree.
When to Use dnd_area
Choose between classic HubL and dnd_area based on who controls the layout.
- Classic HubL (
{% text %},{% rich_text %},{% boolean %}): template author locks the structure, marketers only fill in labelled fields. Use this for brand-critical recurring templates (newsletters, promos, announcements) where design consistency matters more than layout flexibility. Classic HubL templates render correctly in the Remix email editor. - dnd_area: template author provides a starter layout, marketers drag/drop/reorder modules per send. Use when different issues need different structures, or when multiple non-technical marketers need layout flexibility without touching code.
For a single-marketer workflow with tight design control ([Company] today), classic HubL is usually the right default. Reach for dnd_area when layout flexibility per send is more valuable than brand-lockdown consistency.
Required <head> Includes
{{ dnd_area_stylesheet }} <!-- REQUIRED for dnd_area rendering -->
{{ email_header_includes }} <!-- Cross-client rendering -->
{{ reset_css_stylesheet }} <!-- Cross-client CSS reset -->
Constraints
- Only ONE
dnd_areaper email template (HubSpot limit) dnd_rowis NOT supported in email — usednd_section>dnd_column>dnd_module- Minimum width: 624px
- Static HTML (logo, footer) goes OUTSIDE the
dnd_area— locked, not editable per-email - Module defaults are passed as parameters in the
dnd_moduletag
Architecture Pattern
Static HTML (not editable)
├── Logo header
├── Gradient accent bar
{% dnd_area "main", full_width=False %}
├── dnd_section → dnd_column → dnd_module (content)
├── dnd_section → dnd_column → dnd_module (more content)
├── dnd_section → dnd_column → dnd_module @hubspot/email_cta
{% end_dnd_area %}
Static HTML (not editable)
├── Footer (logo, social, CAN-SPAM, unsubscribe)
Pre-place a starter layout. For recurring dnd_area newsletter templates, pre-place default {% dnd_module %} tags inside the dnd_area with realistic starter content (e.g. Featured + 2 Blog Posts + 1 Event + Dev Corner). This gives the marketer a working starting layout instead of an empty canvas.
Section markers on repeatable modules. For repeatable dnd custom modules (blog post, event, industry item), add a show_section_marker boolean field. Turn it ON for the first item in a group and OFF for the rest, so they stack cleanly under one marker and one leading divider. This prevents duplicate 'LATEST POSTS'-style headers when the marketer drops multiple instances.
Static-vs-dnd Horizontal Alignment Gotcha
The bug: In a template mixing a static masthead/footer with a dnd_area, the dnd module content renders ~10px to the right of the static sections — even when both use the same inner padding (e.g. padding: 0 40px). Visible as a misaligned divider/separator line or an off-axis share-row box.
Why it happens: HubSpot's dnd_area_stylesheet (injected via {{ dnd_area_stylesheet }}) adds default horizontal padding to the .dnd-section / .dnd-column / .dnd-module wrappers it generates. Those wrappers sit between your email-container <td> and your module's HTML, so the effective left offset of module content is (module inner padding) + (wrapper padding), while static masthead/footer content is just (td padding).
What does NOT fix it (tried and failed on a real newsletter build):
padding={'top':0,'bottom':0,'left':0,'right':0}ondnd_section/dnd_columnhs_wrapper_css={'padding':'0'}on everydnd_modulefull_width=Falseondnd_areaanddnd_section(still a good idea for other reasons, but doesn't fix the offset)- A
<style>block in the template<head>with!importantoverrides on.dnd-section/.dnd-column/.dnd-module— HubSpot's stylesheet injection wins the specificity war somehow.
What DOES fix it — adjust the static sections, not the dnd wrappers. Measure the offset live in devtools (in the company's case: ~10px), then bump the left (and usually right) padding on every static <td> by that amount so it aligns with the module content. The dnd wrapper's offset is fixed — you match it from the static side.
Concrete pattern that worked (modules use 40px inner L/R padding, wrapper adds ~10px each side):
<!-- Masthead: left 50 (not 40) to match dnd module content -->
<td style="padding: 48px 40px 32px 50px;">...masthead...</td>
<!-- Share row: 50 L and R so the box aligns with module content both sides -->
<td style="padding: 48px 50px 0 50px;"><div>...share box...</div></td>
<!-- Footer divider: 50 L and R so the line matches module dividers -->
<td style="padding: 32px 50px 0 50px;"><div style="border-top: 1px solid #E5E7EB;"> </div></td>
Rule of thumb: don't fight HubSpot's dnd wrapper. Measure the offset once, then pad the static sections to match. This keeps all the module padding logic untouched and doesn't rely on CSS override tricks that don't actually work.
Diagnose 'shifted' or 'off' before fixing. When a user flags an email as 'shifted' or 'off,' identify the specific element first. 'Shifted right' can mean viewport-level centering (usually a client or editor-preview quirk, not a bug) or element-level misalignment between static and dnd sections (the real bug, above). Ask which — don't guess. The wrong assumption burns test-send round-trips.
Pre-placed vs. Dragged Module Width
Pre-placed {% dnd_module %} content is wrapped by HubSpot's editor with different default styles than modules the marketer drags in at runtime. If pre-placed content renders at a different width than dragged content, try hs_wrapper_css={'padding':'0'} on the {% dnd_module %}, or check whether the {% dnd_area %} needs full_width=False to stay inside its parent container's max-width.
Module Paths for dnd Email
Only use modules confirmed to work in dnd email context:
| Module | Path | Works in dnd email |
|---|---|---|
| CTA Button | @hubspot/email_cta |
Confirmed |
| Image | @hubspot/image_email |
Confirmed (in official docs) |
| Email Body (rich text) | @hubspot/email_body |
Testing |
| Raw HTML | @hubspot/raw_html_email |
Testing |
| One line of text | @hubspot/email_text |
Testing |
Do NOT use @hubspot/rich_text_email — this path does not exist and produces "Unknown Module" errors.
Module folder convention. Place custom modules for a dnd_area template in a modules/ subfolder next to the template and reference them as dnd_module path="./modules/name". This mirrors the repo layout to the Design Manager folder structure and makes uploads predictable.
Syntax Examples
Rich text content with default HTML:
{# Example values — use the email background and body text colors from /brain/brand-guide/brand-guide.md #}
{% dnd_section
background_color={'color':'#111111'},
padding={'top':'0','bottom':'0','left':'24','right':'24'}
%}
{% dnd_column width=12 %}
{% dnd_module
path='@hubspot/email_body',
html='<div style="font-size: 16px; color: #FFFFFF;">Default content here</div>'
%}
{% end_dnd_module %}
{% end_dnd_column %}
{% end_dnd_section %}
CTA button (native editor):
{# Example background — use the email background color from /brain/brand-guide/brand-guide.md #}
{% dnd_section
background_color={'color':'#111111'},
padding={'top':'36','bottom':'0','left':'24','right':'24'}
%}
{% dnd_column width=12, horizontal_alignment='CENTER' %}
{% dnd_module path='@hubspot/email_cta' %}
{% end_dnd_module %}
{% end_dnd_column %}
{% end_dnd_section %}
Marketer sets brand colors manually in Button module style tab: the brand guide's email CTA background, button text color, and corner radius.
Image module:
{% dnd_module path='@hubspot/image_email',
img={'alt':'Logo', 'height':32, 'src':'https://example.com/logo.svg', 'width':143},
alignment='center'
%}
{% end_dnd_module %}
dnd_section Parameters
{# Example background — use the card/surface color from /brain/brand-guide/brand-guide.md #}
{% dnd_section
background_color={'color':'#111111'},
padding={'top':'0','bottom':'0','left':'24','right':'24'},
max_width=600
%}
Required CAN-SPAM Footer Variables
{{ site_settings.company_name }}
{{ site_settings.company_street_address_1 }}
{{ site_settings.company_street_address_2 }}
{{ site_settings.company_city }}
{{ site_settings.company_state }}
{{ site_settings.company_zip }}
{{ site_settings.company_country }}
Required Links
<!-- Unsubscribe -->
<a data-unsubscribe="true" href="{{ unsubscribe_link }}">Unsubscribe</a>
<!-- Unsubscribe from all -->
<a data-unsubscribe="true" href="{{ unsubscribe_link_all }}">Unsubscribe from all</a>
<!-- View as webpage -->
<a data-viewaswebpage="true" href="{{ view_as_page_url }}">View as web page</a>
Preview Text
<div id="preview_text" style="display:none!important;">
{% text "preview_text" label="Preview Text" value="Preview text here" %}
</div>
CSS Inlining
Use id="hs-inline-css" on style blocks that should be compiled to inline CSS:
<style type="text/css" id="hs-inline-css">
/* These styles will be inlined on target elements */
td { font-family: Arial, sans-serif; }
</style>
Keep media queries in a separate <style> block (without the inline ID) so they aren't inlined:
<style type="text/css">
@media only screen and (max-width: 620px) {
.mobile-full { width: 100% !important; }
}
</style>
Email HTML Best Practices
Layout
- Always use tables for layout.
<table role="presentation">withcellspacing="0" cellpadding="0" border="0" - 600px max width for the email container
- Single-column layouts are most reliable across clients
- Stack on mobile: Multi-column desktop layouts should collapse to single column via media queries
- Use
align="center"on wrapper<td>to center the email container
CSS
- Inline all critical styles. Email clients strip
<style>blocks unpredictably - Keep a
<style>block in<head>as progressive enhancement, but don't rely on it - Media queries go in their own
<style>block - Never use:
position,float,flexbox,grid,filter,clip-path,calc(),CSS variables border-radiusworks in most clients except Outlook (degrades gracefully to square)background-imageunreliable in Outlook — always have a solidbackground-colorfallback
Typography
- Use system-safe font stacks:
Arial, Helvetica, sans-seriforGeorgia, serif @importGoogle Fonts as progressive enhancement — they render in Apple Mail, iOS, some Android — but always include fallback- For AI Upload: don't rely on custom fonts at all
- Minimum body text: 14px. Recommended: 16px for readability on mobile
- Link colors on light backgrounds must pass WCAG AA (4.5:1). Many brand accents fail on white — define a darker, accessible variant of the accent for links on light backgrounds, and record it in the brand guide
Images
- All images must be publicly accessible URLs
- Always include
alttext,width,height, andstyle="display: block; border: 0;" - Use
widthattribute (not just CSS) for Outlook compatibility - Don't use CSS
filteron images — use pre-made assets in the correct color - Compress images for fast load times
- 60/40 rule: Approximately 60% text, 40% images for deliverability
- Hugging the left edge: wrap an image inside a
<td>in a zero-whitespace table (<td style="padding:0; line-height:0; font-size:0;">) when it must sit flush-left with other siblings. A plain<a><img></a>inside a<td>picks up a leading space from surrounding HTML whitespace in some clients, offsetting the image to the right of other left-aligned elements.
Icons
For newsletter and digest-style emails, use line icons (e.g. Lucide) paired with uppercase section labels rather than emoji. Emoji looks dated and can't match brand voice; line icons give a clean, modern, TLDR-like feel.
Icon workflow: download the Lucide SVG from unpkg.com/lucide-static@latest/icons/{name}.svg, bake the brand accent hex in place of currentColor with sed 's/stroke="currentColor"/stroke="#RRGGBB"/' (use the accent hex from the brand guide), then rasterize to a 40×40 PNG with rsvg-convert -w 40 -h 40. Store both the SVG and PNG side by side in marketing/icons/{category}/, and reference the PNG in email (SVG support is unreliable across clients).
Buttons
- Use the bulletproof button pattern (table-based) for Outlook compatibility:
<!-- Placeholder colors — use the email CTA background and button text colors from the brand guide -->
<table role="presentation" cellspacing="0" cellpadding="0" border="0">
<tr>
<td style="background-color: #333333; border-radius: 12px; text-align: center;">
<a href="[URL]" target="_blank"
style="display: inline-block; padding: 14px 36px; font-family: Arial, Helvetica, sans-serif; font-size: 17px; font-weight: 500; color: #FFFFFF; text-decoration: none;">
Button Text
</a>
</td>
</tr>
</table>
Dark Mode — Gmail iOS (Critical)
Gmail App on iOS is a massive platform and the hardest dark mode problem in email. Read this before building any dark-themed email template.
How Gmail iOS dark mode works:
- Gmail applies a proprietary color inversion algorithm to emails — it modifies BOTH backgrounds AND text colors
- It targets:
background-colorCSS,bgcolorHTML attributes,colorCSS, and<font color="">tags - There is no opt-out. No meta tag, CSS property, or HTML attribute reliably prevents Gmail iOS from modifying colors
@media (prefers-color-scheme: dark)is ignored by Gmail iOS (works in Gmail Web only)color-scheme/supported-color-schemesmeta tags have no effect on Gmail iOS
What Gmail iOS does NOT touch:
background-image(includinglinear-gradient()) — this is the only known way to preserve a background color- Actual images (
<img>tags) — these render as-is
Techniques we tested and their results:
| Technique | Fixes Backgrounds? | Fixes Text? | Verdict |
|---|---|---|---|
color-scheme meta tags |
No | No | Useless for Gmail iOS |
bgcolor on <table>/<td> |
No | N/A | Gmail inverts these too |
background-image: linear-gradient(#color, #color) |
Yes | No | Only reliable background fix |
<font color=""> tags |
N/A | No | Gmail overrides them |
@media (prefers-color-scheme: dark) |
N/A | N/A | Gmail iOS ignores entirely |
The core problem for dark-themed emails: You can preserve dark backgrounds with the gradient hack, but Gmail will still mute/shift all text colors. The result is dark background + washed-out text — which can look worse than letting Gmail do its full inversion (where at least backgrounds and text have consistent contrast).
Recommendation:
- Do not build dark-themed email templates expecting pixel-perfect rendering in Gmail iOS dark mode. It will not happen.
- If you build a dark email, accept that Gmail iOS users will see a color-shifted version. Test in HubSpot's "Preview in email client" → Gmail App Dark (iOS 18) to verify it's at least readable.
- Consider whether a light-themed template would serve better if Gmail iOS is a priority audience.
- Do NOT add
background-imagegradient hacks,<font>tags, orcolor-schememeta tags to "fix" Gmail dark mode — we tested all of these and none produce an acceptable result for dark emails. They create partial fixes that look worse than Gmail's native full inversion.
Dark Mode — Other Clients
- Apple Mail: Respects
@media (prefers-color-scheme: dark)andcolor-schememeta — progressive enhancement works here - Outlook.com / Outlook mobile: Uses
[data-ogsc](text color) and[data-ogsb](background color) attributes when forcing dark mode. These are Outlook-specific, not Gmail. - Transparent PNGs may become invisible on inverted backgrounds — use solid-background versions or test carefully
- For clients that support it,
color-scheme: light dark;in CSS is fine as progressive enhancement — just know it does nothing for Gmail iOS
Outlook Specific
- Outlook uses Word as its rendering engine — most CSS is ignored
- Use
<!--[if mso]>conditional comments for Outlook-specific fixes - MSO properties (
mso-table-lspace,mso-padding-alt, etc.) are valid for Outlook only border-radiusdoes not work in Outlook — buttons degrade to rectangular- Background images don't work in Outlook without VML (Vector Markup Language) hacks
[Company] Brand Adaptation for Email
Since email clients have limited CSS support, adapt the brand system. Pull every color value from /brain/brand-guide/brand-guide.md — never hardcode them into the skill or reuse values from a previous build:
| Brand Element | Website | Email Adaptation |
|---|---|---|
| Background | Brand background color | Solid hex from the brand guide — works in email |
| Font | The brand font (see brand-guide) | Arial, Helvetica, sans-serif or another web-safe fallback stack (with @import of the brand font as progressive enhancement) |
| Gradient accent bar | CSS linear-gradient |
Use a pre-made gradient image (hosted PNG/SVG) or a thin <img> element |
| Gradient text | background-clip: text |
Not supported — use a solid text color from the brand guide instead |
| CTA button | Brand CTA color, solid | Styled <a> with {% text %} fields for URL and copy (see CTA section above) |
| Accent tag | Solid accent bg + contrasting text | Works with inline styles — solid background-color and color on the tag element are reliable across clients |
| Card surfaces | Card surface color with border-radius |
Use the brand guide's card color as a solid bg. Radius works except Outlook (graceful degradation) |
| Border | 1px solid brand border color |
Works inline on <td> |
| Social icons | CSS filter: invert() |
Don't use filter. Host icon PNGs in the correct color and reference directly |
CTA Card Blocks
Only simple card-style CTA blocks from the brand guide translate to email. Variants that rely on CSS gradient backgrounds and ambient glows get stripped by email clients — adapt the brand's card CTA pattern with solid background colors and a bulletproof button (see Buttons above).
Gradient Bar as Image
Since CSS gradients don't work in email backgrounds, create the signature gradient as a hosted image:
- Create a 600x4px PNG with the brand gradient (colors from the brand guide)
- Host it publicly (website or HubSpot File Manager)
- Reference as
<img src="[gradient-bar-url]" width="600" height="4" style="display: block;" />
Base Template + Variants
All [Company] HubSpot email templates use a base template pattern. The shared foundation (header, gradient bar, CTA, footer) lives in one file, and each email type is a variant that customizes the content area.
Existing Templates
marketing/templates/email-templates/
├── email-base-hubspot.html ← Base (DO NOT upload — starting point only)
├── [variant]-email.html ← One file per email type (classic coded, HubL fields)
└── _previews/ ← Static HTML previews (not for upload)
└── [variant]-preview.html
Iterate locally against _previews/*.html before pushing to HubSpot. HubSpot round-trips are slow and obscure layout cause-and-effect. Keep the preview faithful to HubSpot's dnd_area wrapping (<td class="dnd-section"> → <td class="dnd-column"> → <td class="dnd-module">); if a preview doesn't mirror that nesting, fix the preview before debugging layout issues in HubSpot.
Creating a New Email Variant
- Duplicate
email-base-hubspot.html - Rename it (e.g.,
product-announcement-hubspot.html) - Update the template annotations:
- Set
isAvailableForNewContent: true - Update
label(e.g.,[Company] - Product Announcement)
- Set
- Replace the content between
CONTENT STARTandCONTENT ENDwith your email-specific sections - Add any extra responsive CSS classes in the media query
<style>block if needed - Upload to Design Manager (see Upload Instructions below)
What's Shared (don't modify unless updating brand)
- Logo header
- Gradient accent bar
- CTA button section (styled
<a>with{% text %}fields for URL and button copy — marketer edits from sidebar) - Footer (social icons, CAN-SPAM address, unsubscribe, view-as-webpage)
- Base styles (
id="hs-inline-css") and responsive media queries - Preview text module
What Changes Per Variant
- The content area between the gradient bar and CTA
- Any variant-specific responsive CSS classes (e.g.,
.date-colfor a two-column date layout) - The preview text default value
Template Structure
Every email template should follow this structure:
1. DOCTYPE + HTML wrapper
2. <head>
- Meta tags (charset, viewport, X-UA-Compatible)
- Outlook conditional comments (PixelsPerInch)
- <style> block with inline-css ID (base styles)
- <style> block for media queries (responsive)
3. <body> (background color on body + wrapper table)
4. Full-width wrapper table (100% width, centered)
5. Email container table (600px, centered)
a. Logo header (linked to website)
b. Content sections
c. CTA button(s)
d. Footer (social icons, copyright, unsubscribe)
6. Closing tags
Output Format
Output location: marketing/email/templates/[template-slug]/ — confirm the project slug with the user before creating files.
For Each Template, Provide:
1. Complete HTML file
- Production-ready, tested against the constraints above
- All styles inlined on elements
- Progressive
<style>block in head - Responsive media queries in separate
<style>block <!-- EDITABLE: -->comments marking content the user should replace- Placeholder brackets
[like this]for variable content
2. Upload instructions
- Brief notes on which upload method to use (AI Upload vs. coded template)
- Any post-upload adjustments needed in HubSpot's editor
- Image hosting requirements (list any images that need public URLs)
For Design Manager (coded templates):
- Go to Content > Design Manager (or Marketing > Files and Templates > Design Tools)
- Click File > New file
- Select HTML + HubL as the file type
- In "What are you building?" select Template
- Click Template type and select Email
- Enter a file name and click Create
- Paste the complete template code
- Click Publish (top right)
- The template will appear in the template picker when creating new marketing emails
- All HubL editable fields (
{% text %},{% rich_text %},{% boolean %}) will appear in the right sidebar when editing an email
3. Testing checklist
- Preview in HubSpot
- Send test email to yourself
- Check rendering in Gmail (web + mobile) — including Gmail App Dark (iOS 18) preview
- Check rendering in Outlook (if audience uses it)
- Check rendering in Apple Mail
- Verify all links work
- Verify images load
- Check mobile responsive behavior
Checklist Before Delivering
- Read
/brain/brand-guide/brand-guide.md - Template annotations present (for coded templates:
templateType: email,isAvailableForNewContent: true,label) - Max width 600px
- Table-based layout only (no flexbox, grid, floats, positioning)
- All critical styles inlined
- No CSS gradients on backgrounds (use images or solid colors)
- No overlapping elements
- No JavaScript
- No
filterCSS property - Font stack includes system-safe fallbacks
- All images use publicly accessible URLs
- All images have
alt,width,height,display: block,border: 0 - Bulletproof button pattern used for CTAs
- Social icons are pre-made white PNGs (not filtered)
- Gmail App Dark (iOS 18) preview checked — email is readable (colors will shift, that's expected)
- No transparent PNGs that become invisible on inverted backgrounds
- CAN-SPAM compliant footer (unsubscribe link present)
- Responsive media queries in separate
<style>block - Outlook conditional comments included
- Tested at 600px and mobile widths
- No AI slop patterns in copy (see CLAUDE.md)
- Product claims verified against
/brain/truth.md
Subscription Types & List Filtering (Sending)
These rules govern who actually receives an email — separate from how the template is built.
- Set the email's Subscription type correctly. HubSpot's send engine auto-filters recipients by the Subscription type field on the email itself, so list-level opt-in filters are redundant: the list defines the candidate pool, the Subscription type field is the actual gate. The type also determines which unsubscribe link the recipient sees and which subscription gets decremented on unsubscribe. Wrong type = unsubscribes hit the wrong list, a compliance and trust risk.
- Active-list 'subscriber' filters must account for the tri-state model. HubSpot's
Opted out of email: [subscription name]property is null by default (Subscribed / Unsubscribed / Not Specified). A filter for 'subscribers' must useis none of YesAND check the 'Include records where property is empty' box — otherwise never-unsubscribed contacts are excluded from the list.
MCP Tools: HubSpot Dev, Figma & agent-browser
HubSpot Dev MCP (Documentation & CMS)
Use these tools to look up HubSpot documentation and manage CMS assets:
- Search docs — Use
mcp__HubSpotDev__search-docsto find HubSpot developer documentation on email modules, template mark
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