logo

Email error 550 5.2.1: Mailbox disabled or not accepting mail

The mailbox exists but is turned off or set not to receive mail. It is a permanent rejection for that address.

Permanent failure (hard bounce)

What it means

The mailbox exists but is turned off or set not to receive mail. It is a permanent rejection for that address.

Common causes

  • The account was suspended or closed.
  • The person left and the mailbox was disabled.
  • The address is a list or alias that no longer accepts messages.
  • The administrator blocked the mailbox on purpose.

How to fix it

  1. Stop sending to the address.
  2. Remove it from your active lists.
  3. Find a replacement contact if the person still matters to you.
  4. Verify the list so disabled mailboxes are removed before sending.

How to prevent it

Remove the address from your list and verify the rest before the next campaign.

Most bounces come from addresses that were never checked. Verify each address before you send: syntax, domain, mailbox and risk are checked without sending a message. Test a single address with the free email checker or upload a whole list for bulk verification.

Verify an email address free · Clean a whole list · MX lookup · SPF, DKIM and DMARC checker

Frequently asked questions

Is it different from user unknown?

Yes: the mailbox exists but is disabled. The result for you is the same, remove it.

Can it come back?

Rarely. Do not keep sending in the hope that it does.

Other error codes

550 5.1.1User unknown (mailbox does not exist) 550 5.7.1Message rejected by policy (blocked) 550 5.7.26Sender not authenticated (SPF/DKIM/DMARC) 550 5.4.1Recipient address rejected: access denied 552 5.2.2Mailbox full (over quota) 553 5.1.3Invalid address syntax

All email error codes