Help - Authentication problem (pam_stack.so)

[amsch]

Hi!

I get the following error message if I try to login to courier:

 
Oct 22 21:43:15 bane imapd-ssl: Connection, ip=[::ffff:192.168.0.3]
Oct 22 21:43:16 bane imapd-ssl: LOGIN: ip=[::ffff:192.168.0.3], command=CAPABILITY
Oct 22 21:43:18 bane imapd-ssl: LOGIN: ip=[::ffff:192.168.0.3], command=AUTHENTICATE
Oct 22 21:43:18 bane authdaemond: PAM unable to dlopen(/lib/security/pam_stack.so)
Oct 22 21:43:18 bane authdaemond: PAM [error: /lib/security/pam_stack.so: cannot open shared object file: No such file or directory]
Oct 22 21:43:18 bane authdaemond: PAM adding faulty module: /lib/security/pam_stack.so
Oct 22 21:43:20 bane imapd-ssl: LOGIN FAILED, method=PLAIN, ip=[::ffff:192.168.0.3]
Oct 22 21:43:25 bane authdaemond: PAM unable to dlopen(/lib/security/pam_stack.so)
Oct 22 21:43:25 bane authdaemond: PAM [error: /lib/security/pam_stack.so: cannot open shared object file: No such file or directory]
Oct 22 21:43:25 bane authdaemond: PAM adding faulty module: /lib/security/pam_stack.so
Oct 22 21:43:25 bane imapd-ssl: LOGIN: ip=[::ffff:192.168.0.3], command=LOGIN
Oct 22 21:43:25 bane imapd-ssl: LOGIN: ip=[::ffff:192.168.0.3], username=xxx
Oct 22 21:43:25 bane imapd-ssl: LOGIN: ip=[::ffff:192.168.0.3], password=yyy
Oct 22 21:43:28 bane imapd-ssl: LOGIN FAILED, user=xxx, ip=[::ffff:192.168.0.3]

I checked and the file does not exist - how can I install pam_stack.so?

Can anybody please help?