That would solve the issues with my alredy setup accounts. But as mentioned when I create a new virtual email account in ISPconfig3 I get the following error messages when loggin into squirrelmail:
ERROR: Could not complete request.
Query: SELECT "INBOX"
Reason Given: Unable to open this mailbox.
ERROR: Connection dropped by IMAP server.
Query: SUBSCRIBE "INBOX.Sent"
Is there an easy way to uninstall and re-install squirrelmail and postfix?