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ISP Information

Impressionwise 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	Whitelist Signup	AOL support pages AOL Postmaster Blog
AT&T	Postmaster pages	does not offer	does not offer	SMTP errors list Blocklist removal form
Bellsouth (AT&T)		does not offer	does not offer
Charter	Postmaster pages	does not offer	does not offer
Comcast	Postmaster pages	FBL Signup	does not offer	Blocklist removal form
Cox	Postmaster pages	FBL Signup	does not offer	Blocklist removal form
Earthlink	Postmaster pages	Send email to fblrequest@abuse.earthlink.net	does not offer	Blocked users
Excite	Postmaster pages	FBL Signup	does not offer	does not offer
Fastmail		FBL Signup
GMX	mail.com
Gmail	Bulk senders guidelines	FBL FBLFBL Signup for ESPs	does not offer	Troubleshooting
Hotmail (Outlook)	Hotmail
Integra	does not offer	does not offer	does not offer	does not offer
Juno	United Online
Live.com (Outlook)	Hotmail
Mail.com	Postmaster page	does not offer	does not offer	Contact Form
Mail.ru	Postmaster.mail.ru	FBL Signup
Netzero	United Online
Office365	Technet
OpenSRS	Tucows
Outlook	Postmaster Website	JMRPP Signup	does not offer	Outlook support pages
QQ	Postmaster Website	does not offer		does not offer
Rackspace	emailsrvr.com	FBL Signup	does not offer	postmaster@emailsrvr.com
Roadrunner	Postmaster pages	FBL Signup	does not offer	Support Request Page
Synacor		FBL Signup
Telenor		FBL Signup
Terra.com.br		FBL Signup
Time Warner Cable	RoadRunner
Tucows	does not offer	FBL Signup	does not offer	does not offer
United Online	Postmaster pages	does not offer	Whitelist Signup	Unblocking Form
Usa.net	Postmaster pages	FBL Signup	does not offer	IP lookup form
Verizon		does not offer	Whitelist Signup	does not offer
Yahoo	Postmaster Pages	FBL Signup	Yahoo! Mail Bulk Sender Form	Detailed Delivery Advice Postmaster Help
XS4ALL		FBL Signup
Zoho		FBL Signup

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	Sending Limits	Certification	Reputation Providers
AOL		500 emails per connection 100 recipients per message	Return Path Certified
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 (Outlook)	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	500 simultaneous connections
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

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