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. The filter can create problems for e-mail servers and block legitimate e-mail as well as spam. When an e-mail client that runs on your computer delivers messages, it always 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.
The ISPs that block port 25 require their SMTP server to be used instead of the remote SMTP server.
Some ISPs that block port 25 include:
* AT&T
* MindSpring
* BellSouth
* MSN
* CableOne
* NetZero
* Charter
* People PC
* Comcast ATTBI
* Sprynet
* Cox
* Sympatico.ca
* EarthLink
* Verio
* Flashnet
* Verizon
* MediaOne
* Telus
If your ISP is on this list or you believe port 25 is blocked,
Click Here for information about changing the outgoing SMTP port from 25 to 26.
Your are here: Home // Bluehost //
Bluehost Email SMTP Port 25 Blocked
There is a very useful discussion of this, including some 'how to' advice at: http://bit.ly/G46Pm