Bounce email handling

Regardless of ingress method any email that is a bounce notification is routed into the bounce handler via the unified processing pipeline.

Hard bounce

An email that hard-bounces triggers a delete flow that removes it from the system.

• All pending sends are canceled
• All subscriptions are removed
• The mail is removed from the allowlist

Soft bounce

An email that soft-bounces is retried after some time until the retry limit is reached and then discarded.