Retries

A delivery succeeds when your endpoint answers with a 2xx status within 15 seconds. Anything else (a non-2xx status, a redirect, a timeout, a connection error, a TLS error) is a failure and is retried.

Schedule

SpacePost makes up to 8 attempts: the first immediately, then retries with increasing delays after each failure.

Attempt	Delay after the previous failure	Roughly after the event
1	immediate	0
2	5 seconds	5 s
3	5 minutes	5 min
4	30 minutes	35 min
5	2 hours	2 h 35 min
6	5 hours	7 h 35 min
7	10 hours	17 h 35 min
8	10 hours	27 h 35 min

After the 8th failed attempt the delivery is marked failed and no further automatic attempts are made. You can replay it manually.

Things to know

• The webhook-id is the same on every attempt, and the body is identical. The webhook-timestamp and signature are regenerated for each attempt.
• Delivery is at least once. A slow 2xx that arrives after the timeout is treated as a failure, so your endpoint may see the same event twice. Deduplicate on webhook-id.
• Ordering is not guaranteed. A retried email.delivered can arrive after a later email.opened. Use created_at in the payload and never move an email’s state backwards.
• Disabled or deleted webhooks stop receiving deliveries; pending deliveries for them are marked failed.
• Response bodies (first 1 KB) and status codes of recent attempts are visible in the dashboard delivery log, which keeps 30 days of history.

Tip

Return 200 as soon as you have verified the signature and stored the event. Do slow work in a background job. A handler that takes more than 15 seconds will be retried and cause duplicate work.