Deleted emails reappearing!

I keep deleting emails, and they keep reappearing. This is ridiculous, have shut down and restarted, doesn't help. Also, people are saying they are unable to open attachments I'm sending, and I just now noticed that a 15 kb message I sent over 10 minutes ago is still showing as still sending at the bottom of my mail screen... anyone dealing with anything similar, ideas to resolve? I let my emails sit until I have way too many, and to spend all this time deleting 1500 emails only to have them reappear in my inbox as new, unread mail is annoying and stressful. I'm using