Great link to information regarding testing SMTP AUTH: http://qmail.jms1.net/test-auth.shtml To test SMTP AUTH I did the following: [server]# perl -MMIME::Base64 -e ‘print encode_base64(“\000test\@domain.com\000testpassword”)’ AHRlc3RAZG9tYWluLmNvbQB0ZXN0cGFzc3dvcmQ= [server]# perl -MMIME::Base64 -e ‘print decode_base64(“AHRlc3RAZG9tYWluLmNvbQB0ZXN0cGFzc3dvcmQ=”)’ test@domain.comtestpassword Then connect to the server and try putting in the above SMTP AUTH details: [server]# telnet localhost 25 Trying 127.0.0.1… Connected to localhost (127.0.0.1). [...]