This article is from a FAQ concerning SCO operating systems. While some of the information may be applicable to any OS, or any Unix or Linux OS, it may be specific to SCO Xenix, Open Desktop or Openserver.

There is lots of Linux, Mac OS X and general Unix info elsewhere on this site: Search this site is the best way to find anything.

TCP/IP and NFS FAQ

How do I test a smtp connection?

When your GUI mail client doesn't work, you need to know whether the problem is at the server or the client. You could download a different client (Thunderbird, if you are using Outlook or Apple Mail) but why spend that time when you can test from thye command line?

Note that some ISP's won't allow you to make port 25 connections to anything but their mail servers. This is to keep viruses from sending mail.

The lines preceded by numbers are typical responses. The actual response may be different.

 
 $ telnet mail.somewhere.com 25
 Trying 192.168.75.194...
 Connected to smtp.somewhere.com.
 Escape character is '^]'.
 220 smtp.somewhere.net ESMTP Sendmail 8.9.3+Sun/8.9.1; Thu,
 
    12 Oct 2000 04:39:40 -0700 (PDT)
 helo aplawrence.com
 250 smtp.somewhere.com
 mail from: tony@aplawrence.com
 250 tony@aplawrence.com... Sender ok
 rcpt to: foobah@aplawrence.com
 550 foobah@aplawrence.com... Relaying denied
 rcpt to: foobah@somewhere.com
 250 foobah@somewhere.com... Recipient ok
 data
 354 Enter mail, end with . on a line by itself
 test
 look ma no headers!
 .
 250 HA00945 Message accepted for delivery
 quit
 221 smtp.somewhere.com closing connection
 

You might also need to do a

helo mymachine.mymachine.com
 

first, and addresses may need to be in angle brackets: <foo@xyz.com>

Remember: some ISP'S block your outgoing packets, only allowing port 25 to their SMTP server. You won't be able to test any other server if this is true.

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