override default port 995 will not remain checked on outlook 2011

I have had problems off and on for months with my ATT email account access from Outlook or Entourage. I switched to Outlook 2011 in April and it works fine but for some reason or other, I will start having to input my password to get mail. The error message pops up, asks for password, I input it, tell it to save in keychain and then may or may not get my mail. What is frustrating is in account settings the override default port will be unchecked and my password gone. I change the default port back to 995, enter the password, x out, restart outlook and it may or may not work. If i go back to account settings, 9 times out of 10 the password is there but the override button is NOT checked as I had done prior to closing it. In other words, Outlook will NOT let me save the override port in inbound mail. I don't understand this at all. And even more strange is the fact that some mornings I turn my laptop on and there is a string of messages in my inbox from the ATT account!! I can then try to send and receive and get the error message again.
I talked with Microsoft help and they suggested ATT was having serious issues with email and that I just delete the account. I CAN access the ATT mail from the web server.
Outlook works fine with my work exchange account but struggles with my personal att email. I have two of them. ATT and a straight yahoo personal account. It seems it must have something to do with Yahoo???
I am thinking of switching my yahoo accounts to gmail to avoid any further frustration with this override port issue.
any ideas?

Again, there is no rhyme or reason to the mail issue. It works fine about 20% of the time and does not the other 80% and has nothing to do with what I do to the account settings.

Very strange.

Thanks,

f