Can't send outgoing mail from any network but my home network

Did you try changing your outgoing smtp mail server to cwmx.com (case sensitive)? I had the same problem and that was the fix for me and many others.

If you search the forums you will find a ton of posts on this and some easy fixes.

There is the free Gmail (Google) solution.

For $24 per year there is the AuthSMTP solution.

Most POP e-mail systems will allow you to check mail from anywhere, if you have the right password. However, they will only allow you to send mail when they can verify that you are connected through their system. That way, a spammer can't send millions of e-mails by pretending to be you when they are really in Eastern Europe. So you need an SMTP server who will "vouch" for you.

With Google, you can attach your POP e-mail account to Google and use their server to send your e-mail as well. With AuthSMTP, they will authenticate you and you can send your e-mail from anywhere, even if you are not locally connected. This includes you iPhone, your Laptop, etc.