Some failed emails are transient — a relay outage, a momentary DNS hiccup, an over-loaded gateway. Others are permanent — bad address, hard bounce, mailbox doesn't exist. Knowing which is which keeps retries productive and avoids harassing genuine non-deliveries.
Automatic Retries
The platform's relay layer automatically retries certain failure classes:
- Connection timeouts to the relay.
- 5xx responses from the relay.
- Soft bounces (temporary mailbox issues).
- Rate-limited responses (4xx 429).
Default retry schedule: after 1 minute, then 5 minutes, then 30 minutes. After 3 failures the message is marked failed and waits for manual intervention.
Manual Retries
From the log:
- Filter to failed messages.
- Click Retry on individual rows or Bulk retry on selected rows.
- Confirm. A new send attempt is queued; original record retained.
What Not to Retry
- Hard bounces (invalid address) — re-sending fails again and may damage sender reputation.
- Spam complaints — the recipient explicitly marked it as spam. Honour that.
- Unsubscribed addresses — never re-send marketing to opt-outs.
- Repeatedly failed transient errors — at some point accept the failure.
Worked Examples
- Relay outage cleared: Bulk retry the queue of 200 failed messages from the outage window. Most succeed.
- Single customer issue: User's mailbox was full yesterday; today it's not. Retry their password reset.
- Permanent bounce: Don't retry. Update the user's email field, ask them for a fresh address.
- Suspicious pattern: 50 hard bounces in a row from gmail.com — your sending IP may be on a blocklist. Check Postmaster Tools before retrying.