To prevent spam, many ISPs block external outgoing mail servers configured for port 25 (AT&T, Charter, COX, Earthlink, Flashnet, MediaOne, Mindspring, MSN, NetZero, Optimum Online, Sympatico, and Verizon are known to block this port). You can check to see if your ISP blocks external SMTP servers by running a simple test:

1. Click "Start" in the lower left corner of your computer screen.
2. Select "Run" and enter the following:

   telnet://smtp.bizmail.yahoo.com:25

If the port isn't being blocked, you'll receive a response starting with a "220." If you do not receive a 220 response, your ISP is blocking outgoing mail servers, and you will need to change the SMTP port from 25 to 465 (recommended) or 587. Before doing this, make sure Microsoft Outlook checks SMTP authentication:

1. From the "Tools" menu, choose "E-mail Accounts."
2. Select "View or change existing e-mail accounts" and click "Next."
3. Select your Yahoo! POP account and click "Change."
4. Click the "More Settings..." button.
5. Click the "Advanced" tab.
6. Click the "This server requires an encrypted connection (SSL)" checkbox. (This step is not required if you choose to use port 587.)
7. Next to "Outgoing server (SMTP)," change port 25 to 465.
8. Click "OK," then click "Next" and "Finish."

If you continue to have problems, please contact your ISP.