Symptoms
Incoming messages for local mail users are failing with the error 'rejected RCPT <mailuser@domain.tld>: No such email address.'
Description
This error means that the Exim service is unable to locate the recipient for the message. This failure can result from invalid permissions on the local files or directories.
Workaround
To repair the local mail directory permissions, you can use the following script provided by the cPanel software. In the below example, you would replace $user with the cPanel account username that controls the mail user.
/scripts/mailperm --verbose $user
This can also be caused by invalid permissions on the accounts home directory but the above script does not check for this. If this does not correct the error, you will also want to ensure that this is set to 711 if FileProtect is enabled or 755 if disabled.
chmod 711 /home/$user