iMail issue?

I have an iMac with OS 10.6.8. We recently switched to Comcast for our internet provider in January. Since Monday we haven't been able to receive mail onto the computer, all I get is a spiraling icon. We receive mail through the web fine, but all of a sudden it isn't working through the computer. We have a wireless router. Everything is plugged into the computer. I called Comcast and they did troubleshooting from their end and said they couldn't find anything wrong.

Yesterday I wasn't even able to upload images to send, it said it was having problems with the server. Today it uploads images, but it doesn't come back through on on the computer (sending a test message)

If this isn't making sense, please ask away- I'm probably not stating things correctly.

Thanks!