Mailbox disabled — not accepting messages
Production Risk
Medium — repeated attempts to disabled mailboxes are flagged as spam-like behaviour by receiving servers.
The recipient's mailbox exists but has been administratively disabled and is not currently accepting messages. This is a permanent failure for as long as the mailbox remains disabled.
- 1The account has been suspended by the mail administrator.
- 2The user has left the organisation and the account was disabled but not deleted.
- 3The account is temporarily locked due to a policy violation.
Sending mail to a suspended or disabled account on the receiving mail server.
RCPT TO:<disabled.user@example.com> # Server returns: 550 5.2.1 The email account that you tried to reach is disabled
expected output
550 5.2.1 ...
Fix
Suppress the address and notify the sender
WHEN Received as a bounce notification
# Add to suppression list
INSERT INTO suppression_list (email, reason, added_at)
VALUES ('disabled.user@example.com', '5.2.1 mailbox_disabled', NOW());Why this works
Suppressing disabled addresses prevents future delivery attempts and protects sender reputation.
✕ Retry delivery to a disabled mailbox
The 5.2.1 code is a permanent failure; the mailbox will not accept mail until re-enabled by an administrator.
RFC 3463 — Enhanced Mail System Status Codes
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