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Queue vs Direct Send

When to Use

Use this when deciding whether a given email type should be sent immediately or queued. The Mailgun module ships a "Mailgun mailer (queued)" plugin that pushes outgoing mail into Drupal's queue API for cron processing.

Decision

Email type Send mode Reason
Password reset, magic link, OTP Direct User is waiting in the UI; queue delay is unacceptable
Payment confirmation, order receipt Direct Customer expectation of immediacy
2FA code Direct Time-sensitive; expires
Welcome email Direct (or short-queue) UX expectation; queue OK if cron runs every 1-5 min
Daily digest, newsletter Queue High volume, no urgency
Bulk announcement (>500 recipients) Queue Avoid HTTP timeout and rate limits
Webhook-triggered notification Queue Decouple from incoming webhook processing

Pattern

Direct send (default)

// Sends synchronously — request blocks ~100-500ms for API call
$result = $mailManager->mail($module, $key, $to, $langcode, $params, NULL, TRUE);

Queued send

Configure at /admin/config/system/mailsystem: - Sender: Mailgun mailer (queued)

Nothing sends until cron processes the queue.

Hybrid — selective queueing

modules:
  user:
    none:
      sender: mailgun_mail        # direct
  newsletter:
    none:
      sender: mailgun_send_mail   # queued

Speed up queue processing (default hourly is too slow)

*/5 * * * * /usr/bin/curl -s https://example.com/cron/CRON_KEY > /dev/null
# Or run the specific queue
*/2 * * * * cd /var/www && drush queue:run mailgun_send_mail

Known open issues (April 2026)

Issue Impact Mitigation
#3165209 — RequeueException infinite re-claim loop One bad item blocks all queue processing Monitor queue depth; manually delete stuck items
#3346676 — Sandbox-rejected mails requeue endlessly Dev environments hammer the API Don't use queue plugin in dev with sandbox domain

Common Mistakes

  • Wrong: Queueing password resets → Right: User waits in UI for the email; cron delay = bad UX.
  • Wrong: Direct-sending bulk newsletters from a controller → Right: HTTP request times out; use queue or batch API.
  • Wrong: Enabling queue plugin in dev with sandbox domain → Right: Hits issue #3346676; sandbox-unauthorized recipients requeue forever.
  • Wrong: Hourly cron with queue plugin → Right: Up to 60 min latency. Use 1-5 min cron or run drush queue:run more frequently.

See Also