OT: but Sendmail experst please help

[Jim Holland]

On Sat, 4 Feb 2006, WILL HALSALL wrote:

> I had a test message from maps regarding open relays. Our sendmail will 
> accept for deliver messages of the format 
> <will.halsall at hotmail.com%fcot5.farn-ct.ac.uk>  but will not accept mail for 
> deliver with format <will.halsall at hotmail.com>. 
> 
> could one of the sendmail experts please explain how to stop this? below is 
> the telnet session 
 
> rcpt to:<will.halsall at hotmail.com%fcot5.farn-ct.ac.uk>
> 250 2.1.5 <will.halsall at hotmail.com%fcot5.farn-ct.ac.uk>... Recipient ok 

I have never seen the above address format.  A common test is to send to 
say will.halsall%hotmail.com at fcot5.farn-ct.ac.uk, which should be denied 
by default with a current version of sendmail.  However this is a 
different format which I haven't seen being used for relaying.

I tried a similar test to yours on sendmail 8.13 with my own domain and a
known yahoo.com address and found that the message was also accepted,
which was rather disappointing (as it can then lead to bounces being sent
to spoofed senders).  The message ended up being undeliverable because
sendmail looked for the domain yahoo.com%mango.zw and said
"yahoo.com%mango.zw.: host not found".  I am therefore puzzled as to how
your message ended up being delivered to will.halsall at hotmail.com.

I would be interested to know what result you get by running "sendmail -bt"
and then entering at the prompt:

	3,0 will.halsall at hotmail.com%fcot5.farn-ct.ac.uk

If it resolves to will.halsall at hotmail.com then you definitely have a 
problem.  I get the following final output:

parse      returns: $# esmtp $@ hotmail . com % fcot5 . farn-ct . ac . uk . 
$: will . halsall < @ hotmail . com % fcot5 . farn-ct . ac . uk . >

which is clearly undeliverable.  Your nameserver reports NXDOMAIN for the 
domain hotmail.com%fcot5.farn-ct.ac.uk, so I am puzzled as to how the 
message did get delivered.  What does your maillog file say for the message?

Regards

Jim Holland
System Administrator
MANGO - Zimbabwe's non-profit e-mail service