I have just upgraded to 365 Office and can no longer connect with my mail etc ... Using AT&T Yahoo and was able to connect using Outlook 2010, I do not know if I am using an Exchange Serve or POP? Have received multiple responses including :
Can not connect...
530 5.1.1 Authentication required
Using Windows 10 and my set up for Outlook used POP3, with ports of 995 and 465 with SSL.