[ale] Bellsouth Sendmail Fix

[Transam]

On Wed, Jul 02, 2003 at 03:14:34PM -0400, Jeff Brodnax wrote:

> I tried sending email to a friend on aol without the smarthost and it
> was rejected, stating I had a dynamic IP.  I added the
> [mail.bellsouth.net] SMART_HOST and it was delivered with no problem, it
> was picked up by bellsouth and delivered with no problems.

Most likely, the real reason why your mail did not go through is because
virtually all ISPs block traffic from their subscribers to any mail server
other than theirs.

This is to force you to use the ISP's mail server so they can filter out
spammers and other abusers.  This is to prevent their entire subscriber
base from being "Blackholed" by anti-spam lists.

Btw, occasionally an ISP will add an additional mail server but the
boneheads will misconfigure this.  This will result in some mail getting
out and some not and, typically, some getting delayed until the random
assignment of systems (due to a list of either "A" address records or
"MX" mail records) hits on one that works.

Note to those with very tight firewalls:
If your firewall limits which of your ISP's servers to use for mail, DNS,
etc., when they add or change these, things will fail silently.  This
happened to me this past week when an additional mail server was added.

> Jeff

Bob Toxen
bob at verysecurelinux.com               [Please use for email to me]
http://www.verysecurelinux.com        [Network&Linux/Unix security consulting]
http://www.realworldlinuxsecurity.com [My book:"Real World Linux Security 2/e"]
Quality Linux & UNIX security and SysAdmin & software consulting since 1990.

"Microsoft: Unsafe at any clock speed!"
   -- Bob Toxen 10/03/2002
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