windows security box keeps popping up in outlook 2013
Many times that I try to send mail, windows security box keeps popping up in outlook 2013. It asks for credentials and I enter them and click remember credentials and it still comes up again. I went into credential manager in windows 7 and deleted everything and tried it all over and it still occurs. What is going on. This happens to other computer on our network also occasionally.
We use Exchange server. This never happened in 2010 outlook.