[Mimedefang] Question about mail/expn/vrfy/etrn

[Lucas Albers]

Based on another posting I found that sendmail by default requires some
sort of helo:
The default is to not allow a SMTP command that does not include a host name.

http://www.sendmail.org/m4/tweaking_config.html

confALLOW_BOGUS_HELO AllowBogusHELO [False] Allow HELO SMTP command that
does not include a host name.

So even if you do not explicitly configure it, it should require a helo.

>
>> Under what conditions would a mail server not send the following
>> commands
>> on a connection?
>> s32.iglobalcommunications.com [64.143.184.32] did not issue
>> MAIL/EXPN/VRFY/ETRN during connection to MTA
>
> You will see this sort of error message when someone connects to your mail
> server and then disconnects without attempting to send mail.  It could be
> something
> as simple as a network service monitoring program checking the health of
> your mail
> server.  It could also be someone performing network reconnaisance in a
> search for
> vulnerable (<8.12.9) sendmail servers.
>
> Sendmail will log that error message if someone disconnects immediately,
> or
> if they
> issue a HELO/EHLO command and then disconnects.
>
> Chris Myers
> Networks By Design