Mail in Yosemite

Question

After reading all the horrible reviews of Yosemite, I decided to try it out on my older iMac (2008) rather than my current one (2011), both supposedly compatible with 10.10. The unattractive appearance and slow speed aside, I have been stuck on trying to fix Mail. Before I upgraded, I downloaded all my mail because I had not used this computer for awhile, and all was well. But after the upgrade, the preferences were ruined, and I had to reset both home and work accounts. Neither will work. Connection doctor tells me that my home email is connected and operational, but no mail will download although it seemed as though a test email did go out (but to where I don't know). And my work email is a mess. It simply will not stay at the settings I choose even though I keep clicking Save time and time again. It goes back to check the SSL box and changes the authentication method to something other than Password. And I do not have the box checked to do this automatically, figuring that would make it accept the settings I put in. Plus, after I did a test email, all my work email in its inbox disappeared. It's totally blank now. I put in the same settings that now work on my newer iMac and worked when I downloaded before the upgrade.
I'm sure there will be other problems, but I need to deal with one at a time. So glad I did not upgrade on my newer iMac.

Answer 1

Back up all data before proceeding.
This procedure will unlock all your user files (not system files) and reset their ownership, permissions, and access controls to the default. If you've intentionally set special values for those attributes on any of your files, they will be reverted. In that case, either stop here, or be prepared to recreate the settings if necessary. Do so only after verifying that those settings didn't cause the problem. If none of this is meaningful to you, you don't need to worry about it, but you do need to follow the instructions below.
Step 1
If you have more than one user, and the one in question is not an administrator, then go to Step 2.
Triple-click anywhere in the following line on this page to select it:
sudo find ~ $TMPDIR.. -exec chflags -h nouchg,nouappnd,noschg,nosappnd {} + -exec chown -h $UID {} + -exec chmod +rw {} + -exec chmod -h -N {} + -type d -exec chmod -h +x {} + 2>&-
Copy the selected text to the Clipboard by pressing the key combination command-C.
Launch the built-in Terminal application in any of the following ways:
☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)
☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.
☞ Open LaunchPad and start typing the name.
Paste into the Terminal window by pressing command-V. I've tested these instructions only with the Safari web browser. If you use another browser, you may have to press the return key after pasting.
You'll be prompted for your login password, which won't be displayed when you type it. Type carefully and then press return. You may get a one-time warning to be careful. If you don’t have a login password, you’ll need to set one before you can run the command. If you see a message that your username "is not in the sudoers file," then you're not logged in as an administrator.
The command may take several minutes to run, depending on how many files you have. Wait for a new line ending in a dollar sign ($) to appear, then quit Terminal.
Step 2 (optional)
Take this step only if you have trouble with Step 1, if you prefer not to take it, or if it doesn't solve the problem.
Start up in Recovery mode. When the OS X Utilities screen appears, select
          Utilities ▹ Terminal
from the menu bar. A Terminal window will open. In that window, type this:
resetp
Press the tab key. The partial command you typed will automatically be completed to this:
resetpassword
Press return. A Reset Password window will open. You’re not going to reset a password.
Select your startup volume ("Macintosh HD," unless you gave it a different name) if not already selected.
Select your username from the menu labeled Select the user account if not already selected.
Under Reset Home Directory Permissions and ACLs, click the Reset button.
Select
           ▹ Restart
from the menu bar.