12.5.136.141	-	Southwest Airlines (unique sender, no retry)
12.5.136.142	-	Southwest Airlines (unique sender, no retry)
12.5.136.143	-	Southwest Airlines (unique sender, no retry)
12.5.136.144	-	Southwest Airlines (unique sender, no retry)
12.107.209.244	-	kernel.org mailing lists (high traffic, unique sender per mail)
12.107.209.250	-	sourceware.org mailing lists (high traffic, unique sender per mail)
63.82.37.110	-	SLmail
63.169.44.143	-	Southwest Airlines (unique sender, no retry)
63.169.44.144	-	Southwest Airlines (unique sender, no retry)
64.7.153.18	-	sentex.ca (common pool)
64.12.137.0	255.255.255.0	AOL (common pool) - http://postmaster.aol.com/servers/imo.html
64.12.138.0	255.255.255.0	AOL (common pool)
64.124.204.39	-	moveon.org (unique sender per attempt)
64.125.132.254	-	collab.net (unique sender per attempt)
66.94.237.0	255.255.255.0	Yahoo Groups servers (common pool, no retry)
66.100.210.82	-	Groupwise?
66.135.209.0	255.255.255.0	Ebay (for time critical alerts)
66.135.197.0	255.255.255.0	Ebay (common pool)
66.162.216.166	-	Groupwise?
66.206.22.82	-	PLEXOR
66.206.22.83	-	PLEXOR
66.206.22.84	-	PLEXOR
66.206.22.85	-	PLEXOR
66.218.66.0	255.255.255.0	Yahoo Groups servers (common pool, no retry)
66.218.67.0	255.255.255.0	Yahoo Groups servers (common pool, no retry)
66.218.69.0	255.255.255.0	Yahoo Groups servers (common pool, no retry)
66.27.51.218	-	ljbtc.com (Groupwise)
152.163.225.0	255.255.255.0	AOL (common pool)
194.245.101.88	-	Joker.com (email forwarding server)
195.235.39.19	-	Tid InfoMail Exchanger v2.20
195.238.2.0	255.255.255.0	skynet.be (wierd retry pattern, common pool)
195.238.3.0	255.255.255.0	skynet.be (wierd retry pattern, common pool)
204.107.120.10	-	Ameritrade (no retry)
205.188.139.136	-	AOL (common pool)
205.188.139.137	-	AOL (common pool)
205.188.144.207	-	AOL (common pool)
205.188.144.208	-	AOL (common pool)
205.188.156.66	-	AOL (common pool)
205.188.157.0	255.255.255.0	AOL (common pool)
205.188.159.7	-	AOL (common pool)
205.206.231.0	255.255.255.0	SecurityFocus.com (unique sender per attempt)
205.211.164.50	-	sentex.ca (common pool)
207.115.63.0	255.255.255.0	Prodigy (broken software that retries continually with no delay)
207.171.168.0	255.255.255.0	Amazon.com (common pool)
207.171.180.0	255.255.255.0	Amazon.com (common pool)
207.171.187.0	255.255.255.0	Amazon.com (common pool)
207.171.188.0	255.255.255.0	Amazon.com (common pool)
207.171.190.0	255.255.255.0	Amazon.com (common pool)
211.29.132.0	255.255.255.0	optusnet.com.au (wierd retry pattern and more than 48hrs)
213.136.52.31	-	Mysql.com (unique sender)
217.158.50.178	-	AXKit mailing list (unique sender per attempt)
64.233.170.192	255.255.255.240	Gmail.com pool
64.233.184.192	255.255.255.240	Gmail.com pool
216.239.56.240	255.255.255.240	Gmail.com pool
209.226.175.0	255.255.255.0	Bell Canada
64.34.54.0	255.255.255.0	AirCanada (Aeroplan)
216.239.56.0	255.255.254.0	Gmail (based on their SPF record)
64.233.160.0	255.255.224.0	Gmail (based on their SPF record)
66.249.80.0	255.255.240.0	Gmail (based on their SPF record)
72.14.192.0	255.255.192.0	Gmail (based on their SPF record)
145.253.2.0	255.255.255.0	Arcor - Germany (based on their SPF record)
145.253.32.0	255.255.255.0	Arcor - Germany (based on their SPF record)
151.189.0.0	255.255.254.0	Arcor - Germany (based on their SPF record)
151.189.8.0	255.255.255.0	Arcor - Germany (based on their SPF record)
151.189.13.0	255.255.255.0	Arcor - Germany (based on their SPF record)
151.189.20.0	255.255.254.0	Arcor - Germany (based on their SPF record)