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

Mailbox/es 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;

Program Files\MailEnable\Config\

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:Wednesday, October 26, 2016