[GLLUG] Sendmail configuration

[Lachniet, Mark]

Mike's right about having proper looking headers.  I'd add to that - if you only intend to *send* e-mails to real people and real mail servers on the Internet, you'll probably get by with using your ISP's smart host.  
 
However, if you want to receive them as well, you'll probably also want to get a proper DNS name such as mail.deepan.com, and make sure that you also have *reverse* DNS records so that if some does a DNS lookup on your IP address, it will come up with mail.deepan.com as well.  If you don't do that, a lot of mail servers on the Internet will reject your mail outright. In addition to DNS you'll want to change your servers hostname to mail.deepan.com, and also edit your mail config with that information as well.  If you are going to receive mail on that host, make sure you check your mail relaying configuration so that not "just anybody" can send mail through you, or you'll get blacklisted in a week or so.
 
Even then you won't get everyone.  Some ISP's appear to block any mail that clearly comes from a DSL or Cable modem IP range (hence another reason to use your ISP's smart host)  I run a full time mail server from my ACD DSL account (lachniet.com) and its a real pain some times.  For example, SBC Ameritech apparently outright blocks my whole IP range randomly, which has forced my mom to get a gmail account.  Tis annoying
 
Mark Lachniet
Solutions Architect - Security
Analysts International
3101 Technology Blvd. Suite A
Lansing, MI 48910
(517) 336-1004 (voice)
mailto:mlachniet at analysts.com
  

________________________________

From: linux-user-bounces at egr.msu.edu on behalf of Mike Rambo
Sent: Thu 3/20/2008 7:16 AM
To: Deepan
Cc: linux-user at egr.msu.edu
Subject: Re: [GLLUG] Sendmail configuration



Deepan wrote:
> Hi All,
> I am using sendmail via php mail function to send
> emails. However few servers reject my mails with
> the error 'Sender address rejected: Domain not
> found', since mails from my server are sent as
> email at localhost.localdomain. How do I change this
> to a valid domain name ? We only own a public IP.
> we dont really have a domain name, is it possible
> to use IP ?
> Regards
> Deepan

You need to set up sendmail to masquerade as a real domain, like that of
your ISP for example, use your ISP as a smart host to send the mail, and
set up the genericstable feature of sendmail so it will modifiy the mail
headers to make mail sent by apache (or whatever user your php scripts
will appear to run as and thus mail as) to be rewritten to a valid user
from your ISPs perspective. Or at least, those three steps are what I
have done when I need to do such things. I've got about five or six
servers set up to do basically what you're describing and It Works For
Me. That said, I've not spent a great deal of time to see if there is an
easier way and I certainly don't claim to comprehend all of sendmail. YMMV.
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