?????? #12659 ?????? ???????? SIMS@stalker.com
?? ????: Timothy Binder <lists@cyberthorn.net>
????: Re: SMTP outgoing problems
????: Wed, 12 Mar 2003 15:41:05 -0500
????: SIMS Discussions <SIMS@mail.stalker.com>
X-Mailer: Apple Mail (2.551)
On Wednesday, March 12, 2003, at 02:44  PM, Gil Poulsen wrote:

I do find it strange, though, that SIMS would verify return paths for local
users. How could they possibly resolve correctly if local users have
non-routable, DHCP-assigned IPs like 192.168.0.6 or 10.0.1.6? Or am I not
understanding what this function is actually doing?

Verify return paths is based on the Return Path header, which is a user's email address. It is passed to the mail server as part of the "MAIL FROM: user@domain.com" command. SIMS does a lookup on domain.com, not a reverse lookup on the sending IP address. Since domain.com, in the case of local users, is typically the mail server itself, it doesn't have to go actually do a DNS check, since it's locally valid.

Verify return paths is a sanity check more than a security procedure. It will keep spammers from using addresses like <doesnotexist@localdomain.com> and <haksdfj@jadsfhkds>.
--
We're at Code Orange right now and panic is the new black.
-- Paul F. Tompkins

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