Many ISPs are blocking what is called "Port 25" which is the port used to send e-mail. They are doing this to cut down on the amount of spam that is sent from their networks.
All e-mail sent via the Internet is routed through the port 25, the channel used for communication between an e-mail client and an e-mail server. Even though port 25 blocking will probably become an industry standard, however, the filter can create problems for e-mail servers and block legitimate e-mail as well as spam.
Port 25 blocking allows ISPs to block spam sent out through their networks, but it tends to punish the innocent that have a need to send through e-mail servers other than those belonging to their ISP. The ISPs that block port 25 require their SMTP server to be used instead of the remote SMTP server or a SMTP server running on your computer.
How the port 25 is used
All e-mail sent via the Internet is routed through port 25. When an e-mail program that runs on your computer delivers messages, it uses port 25 to transmit data to remote e-mail servers. Therefore, if your ISP is blocking the port, your messages will not get through.
ISPs that block Port 25
This list contains some of the major ISPs that block port 25 on their servers:
|
AT&T (can be unblocked at the request) |
MindSpring |
|
BellSouth |
MSN |
|
CableOne |
NetZero |
|
Charter |
People PC |
|
Comcast ATTBI |
Sprynet |
|
Cox |
Sympatico.ca |
|
EarthLink |
Verio |
|
Flashnet |
Verizon |
|
MediaOne |
|
Solutions
To bypass the port 25 blocking you have these options:
Use the SMTP server provided by your ISP, you will need to contact their support department for this information.
Change your outgoing SMTP port to 26 to use our servers.
