Useful for finding problems with new installations.
- telnet examplemailserver.com 25.
- Key in “EHLO examplemailserver.com” and press enter.
- Key in “MAIL FROM: sender@mydomain.com” and press enter.
- Key in “RCPT TO: recipient@examplemailserver.com” and press enter.
- Key in “DATA” and press enter.
- Optionally add envelope headers (and leave a blank line between these header values and the message body):
From: “me”
To: “you”
Subject: This is the subject line
X-CustomHeader: This is a custom header - Key in your message body and press enter.
- Key in ” . ” and press enter.
- Check the mailbox.
Authentication
For servers that require authentication first encode the username and the password to base64 e.g.
echo myusername | openssl enc -base64
echo mypassword | openssl enc -base64
Then use the returned values when prompted. After the ehlo specify:
AUTH LOGIN
assuming it is supported.
Secure Protocols
The H Security provides info on using openssl to test secure connections to email and web services. So as an example testing SMTP (with STARTTLS) :
$ openssl s_client -host mail.irgendwo.de -port 25 -starttls smtp
CONNECTED(00000003)
[…]
250 HELP
ehlo test
250-Mailserver Hello loki [10.1.2.73]
250-SIZE 52428800
250-PIPELINING
250-AUTH PLAIN LOGIN
250 HELP
and to test IMAPS:
$ openssl s_client -host imap.irgendwo.de -port 993
[…]
* OK IMAP4 Ready 0.0.0.0 0001f994
1 Login user-ju secret
1 OK You are so in
2 LIST “” “*”
* LIST (\HasChildren) “.” “INBOX”
* LIST (\HasNoChildren) “.” “INBOX.AV”
[…]
2 OK Completed (0.130 secs 5171 calls)
3 logout
* BYE LOGOUT received
3 OK Completed
The H Security article also covers POP and HTTPS.
