Cyrus-Imap Server shows “Mailbox is locked by POP3 server” error message in Outlook Express Thunderbird mail clients.
In Cyrus Imap Mail server for a particular user, emails were not received in his email client(Thunderbird).
And the following error message was shown in the email client.
Mailbox is locked by POP3 server
Remove the lock file of the particular user.
In Cyrus Imap Server just Kill the pop3 process of the particular user manually.
And Remove the lock file form the following imap proc folder.
/var/imap/proc/< pid >
In old mail box just remove /var/mail/< user >.lock