No mailbox here by that name error: fix

Introduction

The No mailbox here by that name error, often paired with 5.1.1 or chkuser, means the receiving server did not find a valid mailbox with that name.

In practical terms, you are trying to send to an address that the destination server does not recognize as existing.

Most common causes

• the address is misspelled
• the mailbox was deleted or never created
• an alias or redirect no longer exists
• MX records or routing are misconfigured

How to review it

1. Check the exact address

Verify the username, domain, dots, hyphens and possible auto-complete mistakes.

2. Confirm whether the mailbox exists

If the recipient belongs to your own domain, open cPanel or DirectAdmin and review the list of mailboxes.

3. Review aliases and forwarders

Sometimes the address depends on an alias or forwarder that was removed.

4. Review MX and mail routing

If the domain points to another email service, the local server may not be the right place to look for that account.

Useful tips

1. Do not confuse it with a full mailbox

   Here the problem is usually mailbox existence, not storage space.

2. Test another address on the same domain

   If other mailboxes on the domain work, the problem is probably limited to that specific account.

3. Keep the full bounce

   The exact wording helps distinguish between a nonexistent account and a routing issue.

Frequently asked questions

Is it the same as 550 No Such User Here

Almost yes. The technical meaning is very similar.

Can it be caused by my own mailbox

Usually not. It generally points to the destination address or domain.

Should I simply try again later

Only if you know the mailbox is being fixed. If it does not exist, the error will repeat.

Conclusion

No mailbox here by that name usually means a nonexistent address or a mail route that points to the wrong place.

Reviewing the mailbox, aliases and MX records is often enough to find the cause.