[Mimedefang] Re: mail server not issueing helo ro similar

[Jeremy Mates]

* Lucas Albers <admin at cs.montana.edu>
> How common is it for MTA's to not send a:
> helo or etrn commnad?

Not very common at all; usually these sorts of logs come from monitoring
systems like Big Brother or Nagios that connect to see whether something
is listening, then disconnect without issuing any SMTP commands. Or it
could be someone scanning for services, or a MTA that times out before
being able to do anything. To reproduce the message:

telnet mail.example.edu 25

and then type "quit", and consult the logs for the "did not issue" log.

> Assuming you are using sendmail, will it even accept the mail if a
> valid helo or ehlo command is not received?

That depends on whether 'needmailhelo' is set as a confPRIVACY_FLAGS
option in the sendmail.mc for the server in question.

> Can you reject on this?

I see no reason to, unless a particular hostile host is connect
flooding, in which case firewalling off the host might be required.