ICloud mail account could not be enabled

Question

Since I have updated to Mavericks I have been having difficulty with "Mail".  I had 4 accounts; two of which were gmail accounts.
After reading about the gmail issues, I was hoping that the recent "Mail Update for Mavericks" would solve my issue. Unfortuantely my issues remain.
The problem first began with the program taking minutes (up to 10 min) to load; forcing me to force quit the program many times.
I slowly deleted the various accounts from my icloud account. Interestingly in the System Preferences under "internet accounts" it would initially not display all of the accounts that I had listed in the mail program. It would also take 10 min to load the accounts into the Accounts Pane on the "internet Account" dialog.
Even after deleting each of the accounts; including my icloud account and then only re-enabling my icloud account things didn't get better.
Now "mail" doesn't load at all. And I can't enable "mail" in the Icloud system preferences.
It times out after 3-5 minutes saying "Your iCloud mail account could not be enabled. Try enabling it again". Of course; trying again gets the same message.
So I'm stuck not using "Mail" at all; and I don't know what the issue is.
I've moved on to "AirMail" and it is working fine. But would like to use "Mail".
Any one else getting this???

Answer 1

I had this problem & found these instructions, it worked everything as it was before the upgrade now, except I've lost the old email accounts I deleted.
The problem was caused by dodgy entries in the accounts.plist file in my User Library folder. It appears that either when I upgraded to Mavericks this file gained many thousands of duplicate entries, or maybe these entries were in there before but previously the OSX/Mail combination was more tolerant. When I removed these the problem with Mail disappeared. Here’s what I did….
1> Make the user Library folder visible - in Mavericks this is a lot easier than Lion/Mountain Lion. Simply open up your user directory in Finder, select menu View>Show View Options, and select “Show Library Folder”
2> Navigate through username>Library>Mail>V2>MailData and select the Accounts.plist file. If this file is multiple megabytes (mine was 40+mb) then this is likely the cause of your problem (once sorted mine ended up at 19k in size!)
3> To be safe, make a copy of this file (I placed the copy on my desktop).
4> Using your chosen text editor (I used Text Wrangler but I’m sure TextEdit would work just fine) open the Accounts.plist in the MailData folder (not your backup copy) and take a look. If it’s the same as me you will find hundreds and hundreds of entries for the same mailbox repeated in there. Mine was an old MSN mailbox that I never use any more (I’ve seen in other forums that other Hotmail type accounts also seem to be the culprits in this context). There will likely be two lots of repeated data, one in the XML “DeliveryAccounts” <array> section, and one lot in the “MailAccounts” <array> section.
5> Delete (keeping in mind the need to select the XML sections correctly from <dict> to </dict> completely) all those extra entries that you found, keeping the mail accounts you do need, in the XML and save the file.
6> Mail should open up nice and fast again and not eat your system
7> If this did not work, and causes problems because of over eager deleting in <5> you can replace your broken Accounts.plist file with your backup and try again.