Error: 550 'Requested action not taken: mailbox unavailable or not local' when running Plesk


If a mail server receives a request to deliver a message to a non-existent user, then it will reply with a 5XX series error.

The e-mail client or downstream mail server attempting the send operation will receive this error and will generate a non-delivery message to the user.

The cause of the error is either that the user/mailbox does not exist (and has been specified incorrectly when the user sent the message) or that a server configuration problem is stopping the server from resolving the users e-mail address.


When sending messages through MailEnable the following error is returned in the client:

550 Requested action not taken: mailbox unavailable or not local

Mailboxes are unable to send and receive.

This article only applies to servers running the Plesk Control Panel and can occur with all mailboxes on the system or only one/some.


The Plesk control system has the ability to disable mailboxes within its interface. To do this the panel edits the MailEnable configuration file ( and adds a ! into the mailbox address which makes the mailbox unrecognisable by the MailEnable services.

To verify this is the case, check in the MailEnable Administration program for a mailbox that is experiencing the issue and see if the mailbox is disabled. A mailbox that is disabled within MailEnable will have a red cross on the mailbox icon. 

For more advanced users, or to verify if Plesk was the service that disabled the mailbox, open the following configuration file:


and search for any mailboxes that appear like the following entry:

[!] a normal mailbox would appear without the ! before the SMTP: part of the configuration string.


To resolve this issue, re-enable all the mailboxes within the Plesk control panel, or search through the file and remove all ! characters.


MailEnable response codes:




Plesk Control Panel:

Product:MailEnable (All Versions)
Class:HOWTO: Product Instructions
Revised:Monday, November 7, 2016