Sending & delivery events
Soft bounce
A temporary delivery failure — a full mailbox or a momentarily unreachable server. Soft bounces are worth retrying a few times before giving up.
Common causes
- The recipient’s mailbox is full.
- The receiving server is temporarily down or overloaded.
- The provider is rate-limiting you, often because you sent too much, too fast from a new domain.
- The message is larger than the server accepts.
How soft bounces are handled
Temporary failures are retried automatically over a period of hours, since most clear up on their own. If an address keeps soft-bouncing across many sends, treat it as dead and stop mailing it.
Soft bounces in MailCraft
While MailCraft retries a temporary failure, the email is marked delayed and an email.delayed webhook fires, so you can see retries happening without mistaking them for final failures.
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Start freeRelated terms
Full glossarySending & delivery events
Hard bounce
A permanent delivery failure — the address or domain doesn’t exist. Hard bounces should be suppressed immediately and never retried.
Deliverability
IP warm-up
The practice of gradually increasing send volume from a new domain or IP so mailbox providers build trust in your sending pattern before you reach full volume.
Sending & delivery events
Webhook
An HTTP callback your application receives in real time when an event happens — a delivery, open, click, bounce or complaint — instead of polling for status.