My problem is with gforge-mta-exim4

edit

nano /var/lib/dpkg/status

Search for the gforge-mta-exim4 entry (Ctrl+w followed by gforge-mta-exim4)

Delete the block for gforge-mta-exim4.

updatedb
locate gforge-mta-exim4

delete all the file for gforge-mta-exim4