First you need to convert your username to Base64 $ echo “username” | base64 dXNlcm5hbWUK Next convert your password to Base 64 $ echo “password” | base64 cGFzc3dvcmQK Then you can connect to the server through telnet telnet mail.example.com 587 Trying 192.168.1.100… Connected to mail.example.com. Escape character is ‘^]’. 220 mail.example.com ESMTP Postfix ehlo mail.example.com