TCP/IP filter & SMTP

From: sharky (sharky@nospam.com)
Date: 09/10/02 

From: "sharky" <sharky@nospam.com>
Date: Mon, 9 Sep 2002 19:32:55 -0700

I have enabled TCP/IP filter on all addresses on my web server (yea me).

I've got everything working except the UDP filter. I denied access to all
UDP services except 88,137,138,53,135 which allows me to browse my network
connection to shares, resolve dns, and use RPC - BUT for some reason, my web
server can no longer find my ISP's SMTP server to send mail from our asp
formmail. I get the following error:

WSAHOST_NOT_FOUND

That doesn't seem right because I've got SMTP (TCP) enabled on TCP, and DNS
(53) enabled in UDP, and I can't find any other ports that SMTP might use.

If I enable all UDP ports, it works fine. When I deny all UDP ports except
the above, it breaks, so it must be some UDP port is needed to use SMTP from
my web server.

NOTE: this ONLY happens when I turn off UDP ports, and yes I have enabled
SNTP ports on TCP, but that doesn't appear to be the problem because I only
have this problem when I deny UDP ports.

Has anybody run into this before or have some knowledge on the subject they
can share?

Gracias!

Relevant Pages

  • Re: Most important UDP ports?
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    (Pen-Test)
  • a UDP Exception Problem of Windows Firewall
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  • Re: Allow all "high UDP" or not ?
    ... > My firewall is McAfee Desktop Firewall. ... > a so large range of UDP ports open? ...
    (comp.security.firewalls)
  • RE: Locking down UDP ports
    ... lsof |grep -i UDP ... and if you don't have lsof (why linux distributions don't install it by default??????) try on www.rpmfind.net ... Subject: Locking down UDP ports ...
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  • Re: TCP/IP Filtering Problem
    ... Ensure that you allow UDP 53 inbound and outbound. ... due to it being dependent on DNS. ... Also, sending mail with the SMTP server does not work, and adds ... > When I allow all UDP ports, ...
    (microsoft.public.inetserver.iis.security)