http://askubuntu.com/questions/760026/problem-with-pam-authorization-in-dovecot
in /etc/dovecot/conf.d/10-master.conf uncomment this line; #default_vsz_limit = 256M and increase the vsz_limit. e.g. default_vsz_limit = 512MSeems like a bug/change in the recent build of PAM. Hopefully this helps someone else doing a bunch of fruitless seaching / debugging :)
