OOT: Mail rejected with bogus helo
peter at farrows.org
Wed Apr 16 20:21:55 IST 2008
Matt Kettler wrote:
> Budi Febrianto wrote:
>> Dear All,
>> I know this OOT, but because many sendmail experts in here, I give it
>> a shot.
>> I'm using sendmail-8.13.8-2.el5 with MailScanner 4.65.3.
>> Whenever my users sent emails to certain domains, it will rejected
>> with this error.
>> 553 yyy.yyy.yyy.yyy rejected due to spam, contact 555-505-5555 (bogus
>> helo xxx.xxx.xxx.xxx)
>> I'm not sure what happen, because I don't have the same problem with
>> others domain.
> Your system is issuing a HELO in IP format, which is RFC compliant,
> but some view this as a sign a system isn't properly configured and
> will refuse mail from such systems.
> However, more troublesome is your system is issuing a HELO in IP
> format using a private-range non-routable IP, 10.10.16.24. This is
> blatantly bogus when communicating with hosts outside your network, as
> those hosts will never be able to route to 10.10.16.24 and reach your
> server. (The original intent, although outdated, is for the HELO to be
> usable as a hint for where to return mail to if DNS fails to generate
> a MX or implicit MX record. Generating private IPs here is clearly
> contrary to that.)
> Ultimately, it's up to the administrator of the system you're trying
> to contact to tell you why he's filtering you. Those are purely
> guesses on my part, based on looking at the HELO's your server issued,
> and general knowledge of what some admins do for filtering that not
> everyone does.
I agree, technically its against RFC to block email based on a bad helo
see RFC 2821, however none of the systems I administer will accept an
obviously bogus hello, this is very effective at MTA level in
controlling the entry of spam into the mailscanner.
RFC 2821 >> "However, the server MUST NOT refuse to accept a message for
this reason if the verification fails"
Its up to you how you handle it, but more and more servers will refuse a
bad helo even though technically they shouldn't.
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