First of all i have solved this issue and thougt someone else could find it usefull someday. Out of nowhere one of my servers started to give me random errors like these SASL NTLM authentication failed: authentication failure and : couriertls: accept: error:1408F10B:SSL routines:SSL3_GET_RECORD:wrong version number. I tried to telnet as described in http://www.howtoforge.com/perfect_setup_debian_etch_p5 and i got 250-AUTH=PLAIN LOGIN CRAM-MD5 NTLM DIGEST-MD5 instead of 250-AUTH PLAIN LOGIN Here is how i solved it, my servers running debian Etch. /etc/postfix/sasl/smtpd.conf was missing mech_list: plain login. should look like this: and /etc/courier/imapd-ssl had TLS_PROTOCOL set to =SSL2 changed that to TLS_PROTOCOL set to =SSL23 And I havent got any errors since.