More and more ISP's are starting to enforce their customers to send email only using their SMTP servers. The reason is to monitor spamming activity and prevent regular PCs to directly send emails when contaminated by the malware that convert them into spam spewing drones. 

To check if your ISP is blocking SMTP traffic to our servers by doing the following: 

a) (Windows) START -> Run. Type 'command' (without quotes) and press ENTER 

b) On the screen that opens type the following (subsitute yourdomain.com apropriately) 

C:>TELNET yourdomain.com 25 

If you get something similar to the following: 

220-host.serverdomain.net ESMTP Exim 4.69 #1 Mon, 21 Jul 2008 22:59:23 -0400 

220-We do not authorize the use of this system to transport unsolicited, 

220 and/or bulk e-mail. 

your ISP is NOT blocking 

If you get something similar to: 

C:>TELNET yourdomain.com 25 

Connecting To yourdomain.com... Could not open connection to the host, on port 25 

: Connect failed 

your ISP IS blocking SMTP traffic to our server. 

The immediate solution is to use your ISP's SMTP server as we have always reccomended (even though it works and we provide instructions for using it AMPHION Communications does NOT support SMTP services for our hosting clients) 

A great work arround to the issues of email portability and SMTP service for multiple locations is to use gmail.com as an email gateway for our hosting services. Please read the Knowledge Base article entitled: "Gmail is your Friend" 

At the moment of writing this and testing from our offices in Florida, Comcast was NOT blocking and AT&T/Bellsouth WAS blocking, but those status can change, here is a list that do not intend to be exhaustive, comprehensive or precise. 

ISP's that are known to Block Port 25 

=================================================== 

• AOL: smtp.mail.aol.com 

• Adelphia: mail.adelphia.net 

• Ameritech: mailhost.det.ameritech.net 

• Astound Broadband: smtp.ca.astound.net 

• AT&T: mailhost.att.net 

• AT&T Global: smtp1.attglobal.net 

• Bell internet highspeed (Canadian): smtp10.bellnet.ca 

• Bell south: mail.bellsouth.net 

• bigpond.com (Australian): contact service provider for Settings. 

• Bresnan Communications: mail.bresnan.com 

• BT Yahoo in the UK: contact service provider for Settings. 

• CableOne: mail.cableone.net 

• Charter Communications: smtp.chartermi.net 

• Charter.net: smtp.charter.net 

• CharterTN.net: mail.chartertn.net 

• CharterMI.net: mail.chartermi.net 

• Cinncinnati Bell/Fuse Dial-up: smtp.fuse.net 

• coax.net: smtp.west.coax.net /east / central 

• comcast: smtp.comcast.net 

• Cox: smtp.west.cox.net - smtp.central.cox.net - smtp.east.cox.net 

• Earthlink: smtp.earthlink.net 

• Etisalat (UAE): smtp.emirates.net.ae 

• epix: out.epix.net 

• erols: smtp.erols.com 

• Frontiernet.net: smtp.frontiernet.net 

• fuse: smtp.fuse.net 

• Icehouse.net: mail.icehouse.net 

• iquest.net: mail.iquest.net 

• ISP.com: mail.isp.com 

• Juno: smtp.juno.com 

• Megared (Mexico): contact service provider for Settings. 

• Mindspring: smtp.mindspring.com 

• MSN: smtp.email.msn.com 

• MSN.DSL: secure.smtp.email.msn.com 

• NEBI.com: mail.nebi.com 

• Netcom: smtp.ix.netcom.com 

• NetZero: smtp.netzero.net 

• OOL (Optimum Online): mail.optonline.net 

• Optusnet: mail.optusnet.com.au 

• Pacific Bell (Pacbell): mail.pacbell.net 

• panix.com: mailhost.panix.com 

• PeoplePC: smtp.peoplepc.com 

• Plala: plala.or.jp 

• Quixnet.net: smtp.quixnet.net 

• RCN: smtp.rcn.com 

• Road Runner(NYC): smtp-server.nyc.rr.com (for other states, and regions contact your Road Runner Support team) 

• Rogers Hi-Speed (Canadian): smtp.broadband.rogers.com 

• SBC: smtp.sbcglobal.net 

• SBC Yahoo: smtp.sbcglobal.yahoo.com 

• Shaw.ca: shawmail 

• Speakeasy: mail.speakeasy.net 

• Suddenlink: smtp.suddenlink.net 

• Sympatico: smtp1.sympatico.ca 

• Tedata: smtp.tedata.net.eg 

• Telus: check with ISP 

• The-Beach.net: mail.the-beach.net 

• Verio: smtp.veriomail.com 

• Verizon: outgoing.verizon.net (please note that Verizon FIOS should not have any issues with SMTP blocking, only the DSL or other services) 

• Verizon(alt): smtpout.verizon.net (please note that Verizon FIOS should likely not have any issues with SMTP blocking, only the DSL or other services) 

• Videotron: relais.videotron.ca 

yourlink.ca (Canadian): contact service provider for Settings.