Nov 22 00:29:54 box tpop3d[7280]: auth_pam_new_user_pass: pam_authenticate(user): Module is unknown
In /etc/pam.d/tpop3d, change from
auth required /lib/security/pam_stack.so service=system-auth
account required /lib/security/pam_stack.so service=system-auth
to:
auth include system-auth
account include system-auth
