Outlook deletes account

I am having a lot of problems with Outlook since I installed it in January. I don't know why it keeps on deleting the account without me doing anything, one day it is working fine the next day it is all gone and I have to reinstall all the software. Then it takes forever to sync all the folders specially the sent folders, although that might be because I have more than 50000.

After installing the software yesterday I noticed that when I sent a mail merge if wouldn't go to the outbox but stays in the drafts folder. It is the 1st time that this problem has happened. The other times when I installed it worked fine...do you have any tips of why it is doing this now? and why it keeps deleting the account after 4 weeks?  Also the last time I have to reinstalled ( a month ago) I deleted the cache of the sent items but all the mail I sent since it would not come up updated in the sent items??

Thanks