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That depends on the implementation of the queue. Most queues have a "failed/retry" concept, where they mark failed jobs to be retried in some set future point in time. So one failed job does not hold up your entire queue processing.

> a centralized queue that actually does the mail sending, and retries in case of failure.

A bit like SMTP?

not necessarily, in the first write we can update receipt status as "queued" so queue system can update to "sent" or retry