Frequently Asked Question

My Mail is blocked, what does this code mean?

Last Updated 5 years ago

4xx Errors

These errors are temporary failures, usually the server retries every so often up to max-retry days setting, in our case, its 7 days

421 The server is not available at the moment

422 Mailbox Quota exceeded, you or the recipient needs to delete some old mail to make room

431 This is a server error, a hardware problem likely

441 The other server is not responding, a rare error

442 Connection lost during exchanging data, possibly a filter or even a network issue somewhere

446 This is a loop error, there should never be many hops and is possibly a backend storage error

450 The user’s mailbox is unavailable, may be some quota systems report this, or backend error

451 General transient error

452 Too many recipients or too many messages sent in a short amount of time

471 Usually delayed by a filter, or filter error, like greylisting or some such

These errors are permanent, fatal errors, the servers will not retry to send or accept the message again

500 This is a server error, usually command line error.

501 This is a server error, usually an invalid configuration

503 Server expected authentication

511 Usually this means the server does not recognise the recipients address, check spelling

513 As above

517 As Above

530 Local SMTP Auth authentication error

550 Unknown User

551 Relay Denied, make sure you have your outbound SMTP server set correctly

552 Quota Exceeded, mailbox full, usually this is a temporary error, but some may fatally reject

553 Unknown User, check the details and try again, more common than 550

554 Mail is permanently blocked, by access list or DNSBL, usually for spam or abuse.