El Capitan-Receiving Mail Issue

[Glen]

I downloaded El Capitan today over Mavericks with no problems except for one. In Mail I can send mail, but I can only receive mail now if I go to Mail pref's-Accounts-Advanced, and check the box for authorizing insecure authentication. When checked I can receive email, when not checked I can send but not receive and the connection doctor shows: charter SMTP, connected to server, IMAP connection failed connection. I have called my provider and went thru my settings and it does not seem to be their problem.
Any suggestions or ideas?
Thank you.

 

[honestone]

Seems to be quite a few issues with El Capitan and Apple's Mail Program (glad I use Outlook 2011). Did you download and install OS 10.11.1? That "update"/version has some fixes regarding Apple Mail.

 

[Glen]

Yes I did download the update. It has not helped. One person on another forum stated that because El Capitan probably had more secure encryption, that many ISP's are unable to handle the security until they update their encryption program. I do not know much about that. Am hoping that there is a fix for this because I don't like leaving the "insecure authentication" box checked, although I do not use my email for anything very important other than communication and information.