Email errors can be quite confusing.

“550 no mailbox by that name is currently available” is such an error. It says that there’s no mailbox by that name, but you KNOW it exists. You can’t argue with a machine. It can be very frustrating.

At Bobcares, we often resolve such email errors as a part of our Technical Support Services for web hosting companies.

Today, let’s see the top 5 reasons for this error and how we fix them.

“550 no mailbox by that name is currently available” – Causes and Fixes

Based on our experiencing managing websites, let’s see the main reasons for this error and how our Support Engineers fix it.

1. Incorrect mail permissions

Sometimes, it is possible that the mail configuration files of the domain have incorrect permissions (due to a server migration, backup restore, etc.).

This prevents the mailserver to access the mail directory of the domain and results in this error.

How to fix?

We fix this by correcting the file and folder permissions of the domain.

In cPanel servers, we correct the user permissions using the “fixperms” command.

In our servers we manage, we perform periodic server audits to identify and rectify issues such as inadequate permission of files and missing config file entries.

2. Non-existent recipient domain

At times, the domain to which the mail was sent may not exist. This can result from a typo in the email account name.

You can also see this error when the recipient domain is in disabled, deactivated or expired status.

How to fix?

Check if there is any typo in the recipient email address you’ve given.

We confirm the domain is active and not expired using the command:

whois domain.com

Also, we confirm the domain resolves fine using the command:

dig domain.com

3. Incorrect MX records of the recipient domain

If the MX records of the recipient domain are misconfigured, the sending mail server can’t properly route emails to the recipient address.

Also, If recent DNS changes were made, it will take some time to propagate globally. The domain may be unroutable during this period.

Temporary DNS resolution at sender’s ISP end can make it unable to resolve the recipient domain correctly and hence fails to route emails to it.

How to fix?

Here we verify MX records are set correctly for the recipient domain using the command:

dig domain.com MX

Also, we check the connectivity to the recipient mail server using the below command:

telnet domain.com 25

If we notice any missing MX entries or connectivity issues to remote mail server, then this needs to be fixed at the recipient server end.

4. Incorrect email routing

Sometimes, wrong routing configuration in the mail server can end up in such errors.

The email account is hosted elsewhere(Google Apps) but the domain has mail service enabled in the local server. So the server tries to deliver the emails locally and but can’t find such mailbox.

How to fix?

In cPanel servers, to confirm this, we check the MX of the domain, and if it is not pointing to us, we enable “Remote Mail exchangee” else “Local Mail Exchanger” for domain’s “Email Routing”.

5. Callout cache in Spam filter settings

You can encounter this error when you send an email to a newly created email account with Anti-spam enabled.

Anti-spam filters like SpamExperts maintain the information about the existing and non-existing email accounts in “Callout cache” for few hours. This is to minimize network traffic.

So, when you send an email to a new address, the system looks for this email account in this cache list. If no, such email account is found, it throws the above error.

How to fix?

We can clear the Callout cache from the “Clear Callout cache” section in your Spam filter control panel.

This option varies with the Anti-spam filter that you use.

Once this is done, the system queries the destination mail server directly instead of its own cache to determine if the new user is valid or not.

Conclusion

Examining the maillogs, testing the email routing, checking the mail server settings are some ways we identify and fix the issues. Today, we’ve discussed the top 5 causes for the email error “550 no mailbox by that name is currently available” and different ways to fix it.