Q: Mail keeps rejecting my AOL password

I don't have AOL mail but I can tell you last day or so I kept getting similar requests for iCloud Mail through El Capitan Mail app. Then yesterday I realized my Outlook.com mail I receive through Mail was not syncing with server. I was not receiving new mail because I signed in through Safari to Outlook.com and realized I had messages not read. I never got a password issue, but obviously Mail was not obtaining messages either. What really bugs me about this is that Mail app is a basic function need and up until about Yosemite I never had a bit of trouble with Mail. Now its become very unreliable at times and even for iCloud which you would think Apple could at least get that right? My only suggestion is delete your AOL account and add it back in. This could be a issue not with Mail but with OS X Keychain being corrupted or something. This is my theory because all of my iCloud was affected by the password issue. Funny because my iPhone Mail app continued to get iCloud mail but also seem to fail at getting Outlook mail. I have come to the conclusion that OS's have become so complicated that all of them have glitches almost all the time. You fix one thing and the update breaks something else. I find that with Windows too, there is just too much baked into operating systems and apps. Its all great, when it works.