[TriLUG] sendmail smart-host with auth

[Aaron S. Joyner]

Chad Thomsen wrote:

>Are you sure its not a case of the ISPs are doing reverse DNS checks on your
>mail servers IP?  I just setup a new system here at work and that was the
>case.  The DNS records on the mail servers outgoing IP were no existant so a
>lot of ISPs were dropping any SMTP connection attempts.  This caught me off
>guard as it had been several years since I had setup a mail system and back
>then nobody did reverse lookups but then again back then spam was not an
>issue either.
>
>Chad
>
>On 3/29/06, Aaron S. Joyner <aaron at joyner.ws> wrote:
>  
>
>>Brian Henning wrote:
>>
>>    
>>
>>>Hi Folks,
>>>  I've done some googling on this but so far the solutions seem a
>>>little convoluted, so I'm posing the question to the list in the hopes
>>>of there being some simple answer I just haven't found yet.
>>>
>>>Anyway, lately I've encountered more and more problems related to
>>>sending mail from an IP in a dynamic range [this is my MTA at home],
>>>so I figure the best answer would be to smart-host through my ISP's
>>>MTA. Problem is, in order to help curtail spam, the ISP has started
>>>requiring authentication to send mail.
>>>
>>>How hard is it to configure sendmail (8.12.11) to authenticate for
>>>smart-hosting?
>>>
>>>Tanks!
>>>~Brian
>>>
>>>      
>>>
>>A quick google for 'sendmail smtp auth outgoing' turned up this as the
>>2nd hit:
>>http://efflandt.freeshell.org/sbc-smtp-auth.html
>>
>>I knew the basic answer was "pretty simple", and it's pretty cleanly
>>detailed on that page.  If you run into any problems, post back again!  :)
>>
>>Aaron S. Joyner
>>--
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>>
>>    
>>
Some ISPs will block you for your reverse DNS not matching the same name
you announce yourself as, or not matching an A record that points to the
same address.  Yet other ISPs (such as AOL) have gone to the trouble of
compiling lists of IPs used by broadband providers such as TWTC,
Earthlink, etc and actually block against those lists (the business
customers who, in AOLs view of it, might legitimately be sending mail
"directly", end up in a different IP block).  All of these factors can
conspire against you as a dynamic IP customer, so smart-hosting through
a larger-volume mail server and letting someone else handle the hassle
is the most reliable route.

Aaron S. Joyner