OT: but Sendmail experst please help

WILL HALSALL w.halsall at farn-ct.ac.uk
Tue Feb 7 10:54:04 GMT 2006

Hi Jim, 

At first I thought the e-mail was being delivered but after further 
investigation I don't think this is so. As you say the name generates a dns 
error. After some testing and googleing I was at a loss to see why the 
message was accepted for delivery at all. 

doing the sendmail -bt test gives the output you described and I am at a 
loss on how to stop. 



Jim Holland writes: 

> 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 
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Name: Will Halsall
E-Mail: w.halsall at farn-ct.ac.uk 

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