You may have problems sending email if you use an email address from your Internet Service Provider (ISP) – for instance, @fuse.net or @cinci.rr.com – AND you use a program to check your email (Outlook, Thunderbird, Eudora, etc). This is because you are trying to use your ISP’s outgoing email server from outside their network.
You can solve by setting your outgoing mail server in your email program to use a username and password (authentication). This way, you can send email from any Internet connection without changing the outgoing server settings. Your ISP can verify you are their customer trying to use their outgoing server no matter where you are. This will be in the account setup portion of your email program