After a server restart following a crash. when a user tries to connect the server with an IMAP client (such as Thunderbird or Outlook), it will return nothing. If you try to telnet 143 port to connect to IMAP, and manually issue the "select" command to get folder content, you get a result like this:
In some cases, when the server crashes, the user's mail file information gets corrupted for IMAP folders and views.
Resolving the problem
Run the command "load convert -e- /mail/im01.nsf" to disable IMAP and then run the command "load convert -e /mail/im01.nsf" to enable IMAP to fix the user's mail file (where "/mail/im01.nsf" is alterative)