Hi there, I'm Tim and will be assisting you today. I have over 15 Years as an Engineer and have been with eBay, DoD and many others. I will do my VERY BEST to help you. If you like i can offer remote access and a call. In addition, with any positive rating I will support your question going forward for free.
Sounds like a issue on your mail servers side, when did this start happening and are you able to get in via webmail?
this can also be caused by some miss configuration on the client side. What are you using for mail, outlook?