ISP Information - World Wide

ISP Information

Word to the Wise maintains these ISP reference tables for the benefit of senders and systems administrators working to improve email delivery.
The "Sender Support" table below offers a quick reference to various ISP postmaster pages, FBL pages and unblocking pages. The second table, "Delivery and Filtering Details", lists known connect limits, spam filters and certification services.

Sender Support

ISP	Postmaster site	Feedback Loop	Whitelist	Support
AOL	Postmaster Website	FBL signup pages	Whitelist Signup	AOL support pages AOL Postmaster Blog
AT&T	postmaster pages	does not offer	does not offer	SMTP errors list
Bellsouth	postmaster pages	does not offer	does not offer	unblocking page
Charter	postmaster pages	does not offer	does not offer
Comcast	postmaster pages	Comcast FBL signup page	does not offer	blocklist removal form
Cox	postmaster pages	Cox FBL signup page	does not offer	blocklist removal form
Earthlink	postmaster site	Send email to fblrequest@abuse.earthlink.net	does not provide	blocked users
Excite	postmaster website	does provide	does not provide	does not provide
Fastmail		FBL signup
GMX	mail.com
Gmail	bulk senders guidelines	does not provide	does not offer	troubleshooting
Hotmail	Postmaster Website	JMRPP signup pages	does not provide a whitelist	Hotmail support pages
Integra	does not offer	does not offer	does not offer
Juno	United Online
Live.com	Hotmail
Mail.com	postmaster page	does not provide	does not offer	contact form
Mail.ru	postmaster.mail.ru	FBL Signup
Netzero	United Online
OpenSRS	Tucows
Outlook	Hotmail
QQ	postmaster pages	does not provide		does not provide
Rackspace	emailsrvr.com	Rackspace FBL signup page	does not offer	postmaster@emailsrvr.com
Roadrunner	postmaster site	FBL page	no whitelist provided	contact
Synacor		feedback loop
Terra.com.br		FBL Signup
Time Warner Cable	RoadRunner
Tucows	does not provide	Tucows FBL signup page	does not offer	does not provide
United Online	postmaster pages	does not provide	whitelist application	unblocking form
Usa.net	postmaster website	does provide	does not provide	IP lookup form
Verizon		does not provide	whitelist	does not provide
Yahoo	Postmaster Pages	Complaint Feedback Loop	Yahoo! Mail Bulk Sender Form	detailed delivery advice support request form
Zoho		signup link

Delivery and Filtering Details

A little more information about the specifics of delivery at various ISPs. Note that the "does not publish" for limits means that the ISP has said they have limits, but they do not publish those limits specifically. Many of these ISPs tie sending limits to reputation; IPs with poor reputations have much lower sending limits than IPs with good reputations.

ISP	Connection Limits	Sending Limits	Certification	Reputation Providers
AOL		500 emails per connection 100 recipients per message
AT&T	no published limits	no published limits	Return Path Certified
Bellsouth	no published limits	no published limits
Charter	no published limits	no published limits		no confirmed
Comcast	25 connections per IP address	100 recipients per message	Return Path Certified	Spamhaus Spamhaus ZEN Cloudmark CSI Return Path Reputation Network Blacklist.
Cox	5 connections per IP address	100 messages per connection	Return Path Certified	Spamhaus Zen Return Path DNSBL Invaluement SIP list Cloudmark CSI SURBL Spamhaus DBL Invaluement URI list
Earthlink	does not publish	does not publish	no known certification services
Excite	10 per IP	10 per connection	Return Path Certified	Cloudmark CSI blocklist Spamcop blocking list Return Path Senderscore blacklist internal
Fastmail				Spamhaus XBL Spamassassin
GMX
Gmail	does not publish		not using any
Hotmail	based on the reputation	based on the reputation	Return Path Certified
Integra	no published limits	100 emails per address
Juno
Live.com
Mail.com	very little information available	very little information available		has not published
Mail.ru
Netzero
OpenSRS
Outlook
QQ	1 connection per IP	1 email per connection
Rackspace	very little information available	very little information available	Return Path Certified	has not published
Roadrunner	do not publish	do not publish	Return Path Certified	Spamhaus ZEN Return Path Reputation Network Blacklist
Synacor
Terra.com.br
Time Warner Cable
Tucows	very little information available	very little information available	Return Path Certified	has not published
United Online
Usa.net	does not publish	does not publish	Return Path Certified	Cloudmark
Verizon			Return Path Certified	not known to use
Yahoo		20 emails per connection reputation based rate limiting	Return Path Certified	Spamhaus XBL Spamhaus PBL
Zoho