mail account

my mail account has gone crazy for the past couple of days. First, I can't get it to delete the junk mail in that file; also, it can't seem to send all my messages. I get a message that says something about not being able to send out of my server and I get a couple of different options such as 'try later", etc.

I also have had problems recently trying to get Mail to quit so i can shut down. I have to do forced quit a lot!
thanks in advance for any help you can offer,