Paul Hutchings <(E-Mail Removed)> wrote:
>Well, if only *his* emails to you are being bounced, your config has
>nothing to with the problem, unless he's trying to reply to an address
>with a type in it etc..
>
>The way I would read the bounce, is that he sends the email, and his smtp
>server connects to the pipex mail server and HELOs itself as something
>other than a non FQDN (mum1mr1-a-fixed rather than mum1mr1-a-
>fixed.ispname.com).
>
>It's quite a common tactic to block spam, many viruses/trojans simple
>HELO as an IP address, or "localhost".
Thanks, Paul. Internet communications remains a black art to me, so
terms like HELO and FQDN leave me cold. But the gist of your reply
('it's down to him, not you') squares exactly with another response I
had elsewhere. I'll copy it below for interest. (The remaining problem
of establishing whether this really *is* the cause is hampered by the
problem itself. Rather like the familiar Catch 22: "Can you all hear
me at the back?"!)
>Ironic really as we blocked some mail from 123reg yesterday as they
>HELO'd as localhost which is not a FQDN.. and who have they just been
>taken over by :-)
I dearly wish I had the technical nouse to grasp the irony <g>.
--
Terry, West Sussex, UK
====================
Reply from Ralph Fox
--------------------
Your friend is probably uploading the email to his ISP's mail
server to be sent to you, like this diagram [best viewed using
a fixed pitch font]
+--------+ +----------+ +--------+ +-------+
| | | Friend's | | Your | | |
| Friend |---->| mail |---->| mail |---->| You |
| | | server | | server | | |
+--------+ +----------+ +--------+ +-------+
_If_ this is correct [check this with your friend!], then the
problem is as follows
1. Your ISP's mail server requires that the friend's mail
server should give it's (friend's mail server's)
fully-qualified domain name (e.g. "mta4.isp.in") when
the friend's mail server connects to your ISP's mail
server to send the email.
As to why your ISP's mail server requires this, it is to
cut down on spam.
• Almost all bona fide mail servers do give their
fully-qualified domain name when sending email.
• On the other hand, a lot of spammers will send spam
directly from their PC to your mail server [see #3],
bypassing the spammer's own mail server. Often the
spammer's PC will _not_ give a valid fully-qualified
domain name.
2. However, your friend's mail server would seem to be a
rare exception to the mail server rule. It seems that
your friend's mail server is _not_ giving a valid
fully-qualified domain name.
Because of this, your ISP's mail server refuses to
accept the email, believing it to be from a spammer.
The email bounces back to your friend.
3. This is how a lot of spam arrives.
+--------+ +--------+ +-------+
| | | Your | | |
|Spamming|--------------------->| mail |---->| You |
| PC | | server | | |
+--------+ +--------+ +-------+
If your friend's mail server does not give a valid fully-qualified
domain name, then your ISP's mail server assumes the email
is from a spammer. Almost all of the time this will be a good
bet.
|