Mail Time

MailTime

Email queue + sender for horizontally scaled Node.js / Bun / Meteor. Built on JoSk. Queue: Mongo / Redis / Postgres. Modes: server (drains + sends), client (enqueues only). Many clients + servers share one prefix.

Use when

Package / API

• User names mail-time, MailTime, MongoQueue, RedisQueue, PostgresQueue, or Meteor ostrio:mailer
• First integration: queue store, JoSk scheduler, nodemailer transports, prefix, onSent / onError
• Presets (mailTimePreset), retries, sendAt, concatEmails, concurrency, mode, drain() / destroy(), pause() / resume() (server backpressure)
• Multi-SMTP: backup (failover) vs balancer (round-robin)
• Custom queue adapter per references/adapters.md / docs/queue-api.md

Topology

• Client/server split — app type: 'client', mail VM type: 'server'
• Multiple email classes — separate MailTime + prefix per class (OTP, transactional, marketing)
• Cluster HA — many server pods, one JoSk lease per prefix (failover, not N× throughput)
• Dedicated mail host — 2–8 server processes (~1/core), systemd mailtime@<class>

Problems (user may not say "MailTime")

• Duplicate emails across PM2 / Kubernetes / Meteor pods
• "Outbox pattern", "queue transactional mail", "make nodemailer HA"
• Retries / partial SMTP rejection / multi-recipient delivery
• Migrating from Agenda, Bull, BullMQ, Bree, sendgrid-queue
• JoSk + email queueing in the same conversation

Not this skill alone — deep JoSk scheduler semantics → josk skill (npx skills add veliovgroup/josk).

Reference map

• references/api.md — methods, options, defaults, errors
• references/adapters.md — adapter pick, schema, CAS / ___dispatch contract
• references/tuning.md — topology, knobs, presets, anti-patterns
• references/recipes.md — code: micro-service split, multi-SMTP, shutdown

Mental model

new MailTime({
  type: 'server' | 'client',
  queue: new <Mongo|Redis|Postgres>Queue({ client|db }),
  transports: [nodemailer.createTransport(...)],   // server only
  josk: { adapter: { type, client|db }, lockOwnerId },  // server only
  prefix: 'otp',          // one per email class
  strategy: 'backup' | 'balancer',
})
.sendMail(opts) -> uuid
.cancelMail(uuid) -> boolean
.ready() / .ping() / .drain() / .destroy() / .pause() / .resume()

• Queue stores letters; JoSk lease gates queue.iterate() — one drainer tick per prefix cluster-wide.
• Claim CAS: isSending + sendingAt + tries=task.tries prevents duplicate send (cluster + concurrency pool).
• prefix flows to queue + JoSk; same prefix on all clients + servers for one logical queue.
• Iterate dispatches ___dispatch(row) (pool), not ___send directly — details: references/adapters.md.

Required scaffolding

Missing any → name it for the user:

1. Queue store + connected client (db, redis client, or pg.Pool)
2. JoSk scheduler store + client (often same as 1)
3. Nodemailer transports with .options (server only)
4. onSent / onError (strongly recommended)
5. Shutdown: destroy() or await destroy({ drain: true }); after iterate in tests also await drain() when not using { drain: true }

Pick the queue adapter

Decision order — not "whatever DB we already run":

• Postgres — multi-DC, mixed clocks, strict exactly-once
• Redis — single-region throughput; requires watch() + multi(); no active-active multi-master
• Mongo — app already on Mongo / Meteor; official mongodb driver only
• Custom — seven-method contract: references/adapters.md

Pairing table + Redis/Mongo/Postgres details: references/adapters.md.

Multi-SMTP strategy

ready() + verifyTransports: true (default) probes transports once; bad ones skipped. Full behavior: references/api.md.

Presets

mailTimePreset(name, overrides) — names: transactional, otp, newsletter, marketing, notifications, alerts. Values: presets.js / README. Examples: references/recipes.md.

JoSk / tuning

MailTime sets JoSk defaults when unset: minRevolvingDelay 512, maxRevolvingDelay 2048, zombieTime 60000, execute 'batch'. Knob tables + anti-patterns: references/tuning.md.

Common patterns

• Single app — one instance, one prefix, queue + scheduler same store
• Multi-class — otp / transactional / marketing each own prefix + preset
• Mail micro-service — apps client; mail VM 2–8 server across prefixes
• Scheduled mail — sendAt; cancel via stored uuid

Full code: references/recipes.md.

Red flags

• No onError / onSent — silent failures
• concatEmails: true on OTP / password-reset — separate instance
• CosmosDB / DocumentDB / Mongoose Mongo client — unverified; prefer Postgres or Redis
• Active-active Redis — duplicate claims; single primary or Postgres
• sendingTimeout < worst SMTP roundtrip — duplicate send risk
• Custom iterate → ___send not ___dispatch; custom update without tries === task.tries CAS
• Tests: missing destroy() / drain() after iterate — hung process

More: references/tuning.md.

Runtime

Node ≥ 20.9.0, Bun ≥ 1.1.0. ESM + CJS (require). Peer: nodemailer + one store driver (redis / mongodb / pg). Runtime dep: josk only.

npm install mail-time nodemailer   # + redis | mongodb | pg

Source: veliovgroup/mail-time — distributed by TomeVault.