SMTP testing from the command line

To test SMTP from the command line:

1. telnet host-to-test 25 (connect to port 25 on mail server)
2. HELO sending-host
3. MAIL FROM: foo@foo.com
4. RCPT TO: bar@bar.com
5. DATA
   
6. (enter one blank line after DATA)
7. Subject: test
   To: to-user
   From: from-user
   (enter one blank line after From:)
   test text for email
   . (enter a single period by itself on the last line)
8. QUIT

Read on for testing servers that use SMTP AUTH...

To test SMTP with SMTP AUTH (no TLS/SSL) from the command line:

First, use a Perl one liner to compute the Base64 encoded user ID and password needed to authenticate to the mail server. This requires the Perl MIME::Base64 module.

perl -MMIME::Base64 -e 'print encode_base64("00userid00password")'

The output looks something like this:
AHVzZXJpZABwYXNzd29yZA==
Copy the output string so it can be pasted into the AUTH step below.

1. telnet host-to-test 25 (connect to port 25 on mail server)
2. HELO sending-host
3. AUTH PLAIN Base64-encoded ID/password
4. MAIL FROM: foo@foo.com
5. RCPT TO: bar@bar.com
6. DATA
   
7. (enter one blank line after DATA)
8. Subject: test
   To: to-user
   From: from-user
   (enter one blank line after From:)
   test text for email
   . (enter a single period by itself on the last line)
9. QUIT