So, you have to administer some sort of mail system and some user is saying that they can’t send email to some address. You need to try and work out where the problem is — what you’ve got to do is try and send email to that address through a telnet session with their mail system. Now read on …
First look up where you are going to send the email to. Look up the MX record for the recipients domain using nslookup or www.dnsstuff.com. Now launch a telnet session to that address on port 25:
$ telnet 192.168.1.1 25
The mail gateway should respond with code 220 and some welcome message. Now type HELO and the domain name you are trying to send from
HELO noserude.com
The gateway should respond with code 250. Next type MAIL FROM: and the address of the user who is trying to send:
MAIL FROM: nigel@noserude.com
Again the gateway should respond with code 250. Now type RCPT TO: and the address you are trying to send to:
RCPT TO: dave@monkeymad.com
If you get a code 250 here you have shown that it is possible to send an email as this user to that address through your mail gateway, at this particular moment in time at least.
If you don’t want to actually send a mail, because you haven’t told the recipient that you are doing testing, then now is the time to quit with the regular telnet interrupt <ctrl>[
Otherwise type DATA and then type your message, finishing with a dot on a line by itself and a final carriage return. It is polite to put Subject: as the first line, but you probably don’t need to.
Subject: Just a test
This email just a test ...
.
Be real careful here because you have no screen buffer — every character you type is sent in the email so backspace isn’t going to erase your errors.
One final tip — if your mail system is some bit of proprietary software rather than plain old sendmail or exim, then you might be able to send mail with telnet but the problem could still be at your end. I saw this recently with Clearswift MIMEsweeper running on our outbound server. Just because you have demonstrated you can send mail from your box doesn’t mean you can send mail through the mail system on your box — just a thought …
0 Comments