[olug] Sendmail

[Jon H. Larsen]

On Mon, 14 Nov 2005, Craig Wolf wrote:

> Date: Mon, 14 Nov 2005 10:27:20 -0600
> From: Craig Wolf <CJWolf at mpsomaha.org>
> Reply-To: Omaha Linux User Group <olug at olug.org>
> To: olug at olug.org
> Subject: [olug] Sendmail
> 
> How do I tell if sendmail is setup to NOT be a relay?  I did an rpm
> install from Yast/SLES 9 CD and then ran an update to patch it but I
> don't know where/what to check to make sure I have not opened up a
> hole...
> 
> Thanx!!
> 
> Craig Wolf
> Linux Web Server Support
> Desktop/Network Specialist
> 402-894-6283

Craig,

Do a real-life test.

Try connecting to it from an IP address not on your relay list.

telnet sendmail.box 25
helo mybox.something
mail from: email at localdomain.ng
rcpt to: email at outsidedomain.ng
data
To: email at outsidedomain.ng
From: email at localdomain.ng
Date: Email Date Format
Subject: Some subject
Type some stuff.
.
quit

Replace the email addresses and domains with your real ones and see what 
happens.

Trying to send mail from an outside IP not on the relay list will block 
the outgoing mail.

You access file holds your relay options (at least on Fedora/CentOS/RH it 
does)

If might look like this:

#
# /etc/mail/access
#
# Rebuild:
# makemap hash access < access
#
# This file contains the hosts we will relay
#
#

# allow my local networks
192.168.0       RELAY
192.168.1       RELAY
192.168.2       RELAY
192.168.3       RELAY
192.168.4       RELAY



Jon L.

-- 
Jon H. Larsen  - relayer -at- levania -dot- org
Omaha Linux Users Group - http://www.olug.org/
AnimeSunday.org - http://www.animesunday.org/
ICQ#: 10412618 - http://www.levania.org/~relayer/
GPG/PGP Pubkey - http://www.levania.org/~relayer/relayerpubkey.txt