Outlook not working - cannot send

I have a similar situation.  I've been using Outlook on every computer in the office and Outlook has worked fine, ever since the initial installation 4 years ago.  To be honest, my incoming settings and my outgoing settings are different, in that I use my vanity host domain name to get incoming mail, and Comcast to send outgoing mail from my office computers.  These settings worked fine until they upgraded their mail servers over the weekend.  

Without notice from Comcast I am no longer able to send outgoing email via Outlook, using smtp.comcast.net in my sttings.  When I called to explain my situation, I was told that I was using their email server against their Terms Of Service (TOS) all along, and that I would no longer be able to do so.  

I'd like to know what my options if any, might be.  Next step is finding another ISP.