Many DSL and cable Internet providers block use of port 25 outside of
their own e-mail server. That is, if you use Yahoo! DSL, then the only
outside machine they allow you to use for SMTP is the mail.yahoo.com
The best solution I've found is looking for a secure connection to the
*.edu server. Using an SSL connection for SMTP typically uses Port
465, and because it require authentication, few ISPs block its use.
Check with your e-mail provider for available SSL connection settings.
If they don't offer any SSL connection, you can use the ISP's
connection from home.
The reason for blocking standard SMTP ports is to reduce spam and
other misuses of e-mail -- traditional SMTP requires very little