Can receive email but can't send, using Mediacom mail (mchsi)

I have a .mchsi.com email account that I have been using with my mac for a couple of years. All of a sudden when I started send emails it tells me "Cannot send message using the server Mediacom mail" The SMTP server mail.mchsi.com doesn't support authentication.

It says it's offline. I don't understand how to get it back online (I can still send via there online server) I tried delating my account and setting it up again, however all that I got out of that were all my emails were deleted (if anyone knows how to get these back I would appreciate that as well)

Thanks for any help.