Following error appears in the bounce back message while trying to send out an email :
550 Requested action not taken: mailbox unavailable or not local
This issue can be resolved in the following way :
1) Log in to the windows server with RDP( Remote desktop)
2) Start-> Run -> cmd
3) cd %plesk_bin%
4) mchk.exe –domain –domain-name=
mchk.exe is an utility which allows you to restore mail server configuration based on the data stored in the Plesk database.