Recently created mail boxes might fail to receive due to verify cache
In !279 (merged) there was a setting added
address_verify_sender_ttl = 15686s.
This has an unwanted side-effect. If you send mail to an not-existing (even local) address, the error is stored in cache for about 4.5 hours.
Even when you in the meantime create a matching alias/forward/mailbox all mails will be rejected due to the verify cache being read. This should be reverted to the postfix default (0s - disabled).
See #5772 (comment 82507) for details.