The message that appears when an Outlook client is open is similar to:
Enter Network Password
Server: smtp.yahoo.com (sometimes it says pop.yahoo.com)
Username: [my user's yahoo address]@yahoo.com
[ ] Save this password in your password list
I have researched this issue for a couple of years, with no good explanation, and no solution. This error happens with multiple different POP email accounts on multiple different POP email providers (Yahoo, Gmail, etc.) when connected to the internet via multiple different ISPs (Comcast, CenturyLink), using different versions of Windows (XP, Vista, 7, and now 8), and different versions of Outlook (mostly 2007, 2010). I have tried various different account definitions for the POP accounts within Outlook (server names, ports, security settings suggested by the POP mail providers). I have also made different profiles in these Outlook versions and profiles that contain only one POP account). Best of all, the error is not consistent! Some days, users report no problems. Some days, it's like a bulldog that won't go away.
I have contacted the POP mail providers Google and yahoo. I have contacted 2 ISPs (Comcast and CenturyLink). I have reinstalled Outlook clients on various computers. I have verified that the login user names and passwords work well when directly logging in to the POP email accounts via browsers.
I wonder if any advanced Outlook masters on our forum would analyze this issue and document an explanation for why it happens and where members should focus their attention? Perhaps a thorough diagnostic approach? There are many, many posts about this problem in lots of different forums, but I have never seen a definitive explanation or suggestions for cures. Who is up for this challenge? From what I've researched, one could become famous for addressing this!