CANNOT SEND EMAILS but I can receive.

[jjhelvey]

I cannot send emails, it tells me that it sent but it's lost somewhere in cyberspace because the recipients never get them. Has been occurring for months now and I just noticed. How do I fix this? I have tried, several times, to reconfigure the accounts but that doesn't fix the issue. I have downloaded the latest 2.5 upgrade or "fix" but that too didn't fix the issue.