pam_lastlog not supported?

[francis picabia]

I saw a reference in an older question to pam_lastlog.
This would be very useful for pruning out unused accounts.

I'm using saslauthd, and it points to PAM.
In /etc/pam.d/imap I add:

session     required	  pam_lastlog.so silent

This is the only entry I have for session.
Then login by imap and try last command - nothing new showing.

Am I doing this wrong or is it not supported?