So I just did a clean install of the GM of El Capitan. iCloud transferred my internet accounts. Mail, Twitter, Facebook and the like. I had to enter passwords in Internet Accounts Preference Pane for all the Mail accounts. But when I opened Mail the only account showing was my iCloud Mail account. I tried to enter them in Mail preferences but was notified that the accounts already existed. I had to delete the Mail accounts (both gmail and Yahoo) from Internet accounts and then add them in the Mail Application. Any one else have this issue?
While I was able to work it out I am not sure a new user would know how to add accounts in the Mail preferences.
While I was able to work it out I am not sure a new user would know how to add accounts in the Mail preferences.