E-mail server keeps logging me out

I get logged out of my e-mail account mail@juniorchurch.com after around 1 - 2 minutes with the error message Your session has expired. Please log in again. (Error-ID: 728012954-1026333). I have tried several computers using different browsers but always have the same problem. I loose any e-mails I am composing which is extremely frustrating. 

I posted this problem a few weeks ago but I can't find original post. Please feel free to log into my e-mail account at any point to investigate.

Phil