Email queue

The Email queue tab in Components → Sendex builds and sends letters to subscribers.

Building the queue

1. Open Components → Sendex
2. On Email queue select a newsletter in the dropdown and click Add to queue

Each subscriber gets an sxQueue row with a snapshot of mail headers. The body is rendered at send time from the newsletter template (compact mode: empty email_body in the queue).

Duplicates are skipped by row hash.

Events: sxOnBeforeAddQueues (cancellable) and sxOnAddQueues.

Manual send

Action	Description
Send	Send selected rows
Send all	Send the entire queue
Remove / Remove all	Drop queue rows without sending

Manual send from the manager stops on the first error (stopOnError: true).

Single message pipeline

1. Atomic claim: row gets claimed_at, attempts++, expires_at (+900 sec)
2. Render body from template with newsletter, subscriber, user, profile placeholders
3. Event sxOnBeforeQueueSend — plugin can cancel (row removed, no requeue)
4. Send via PHPMailer
5. Success — row deleted, event sxOnQueueSend
6. Failure — claim released, event sxOnQueueSendFailed, retry on next run

After a batch — event sxOnQueueFlushComplete.

Claim and retry

Result	Queue row	Event
Success	deleted	sxOnQueueSend
BeforeQueueSend cancel	deleted	—
SMTP error	claim released, retry	sxOnQueueSendFailed
Plugin skip (false)	deleted	—

Parallel cron workers cannot send the same row twice — atomic DB claim.

Cron

Add a cron job from the MODX site root:

php core/components/sendex/cron/send.php

Frequency depends on subscriber count and hosting limits. Default batch size: 100 emails per run.

Change the limit with system setting sendex_queue_limit — transport does not create this key; add it manually if needed. See System settings.

Example cron entry (every minute):

* * * * * php /path/to/modx/core/components/sendex/cron/send.php

Cron uses the same pipeline as Send all, but does not stop on the first error and logs failures to the MODX log.

Manager send vs cron

	Manager “Send to subscribers”	Queue + cron
Build queue	yes	manual or Add to queue
Send	immediately	on schedule
Stop on error	yes	no
Batch limit	all queue rows	sendex_queue_limit (100)

Related

• Subscriptions — create newsletter and Send to subscribers
• Events — queue hooks
• System settings — sendex_queue_limit