Unable to lock mailbox on Plesk
Email error: "Unable to lock mailbox" on Plesk/Windows server
This can occur when the hostname is incorrectly set in MailEnable (the mail server used by Plesk). To add the correct hostname, you must use remote desktop to access the console (this can't be done through Plesk).
First do the following.
Click Start->(Click)run->(type)cmd.(Click Run).
Now, in the command prompt type the following.
cd %plesk_bin%
From there run the following command.
mchek --all --fix=all
Wait for it to finish and it should run as normal
Also another fix for SMTP issues on Plesk 7.5.3 windows
Go to start->All Programs->Mail Neable->(click)MailEnable Administrator
When that's running do the following.
Click [+]-MailEnable
then Click [+]Mail Enable Management
Click [+]-Servers"
Click [+]-Localhost
Click [+]-Connectors
right click "SMTP" then go to "Properties"
After you've completed that you will need to find the exact hostname of the box. Example (2k3s-221-28 -221-228 last numbers of the IP address.)
Now put the 2k3s-221-28.aspadmin.net (aspadmin.net = domain of where it's at) into the "Local Domain Name:". Click "Apply" and click "ok" close MailEnable" and (Logged in as 'root' on the Windows 2003 server, right click the "Plesk server control" icon in the tray go to click "Control Panel" then when that's open click the check box next to "Mail Server" and on the right hand side click "Restart" it should all work again, no errors.