What is it with Mail app on Mavericks 10.9.2?

Question

This has been an ongoing frustration since I updated to Mavericks, I had no idea it had any relationship with this upgrade until I started reading. First, I read that the issue was being originated when having a Gmail address on Mail, I followed some steps (they didn't make much sense to me, but I did it anyways), where I had to delete all accounts and the follow step by step, I had to add my Gmail account first, then the rest. Problem persisted, I deleted my Gmail for good from my Mail app. For about 2-3 days my iCloud/me account worked with no apparent issues, until, of course when I have the most work to do, ALL my emails stay in Outbox and no matter how many times I ask the system to bring all accounts online, perform all diagnostics, follow any number of forum directions, my account won't work. I have opted for online webmail instead but all my emails on my Outbox are still there, there's no way I can transfer them to my drafts folder so that I can send them out through webmail. Whenever I try doing this then my emails disappear and all my hours of work with them.
It's been an ongoing problem for at least 3-4 months now with good periods of 2-3 weeks with no apparent problems.
I need help I can't work and I also don't like the webmail app, it doesn't allow me to multitask as I usually do on Mail.
Anyone????

Answer 1

Try one of these options. They both give you a clean start with Mail.
1) Create a new User. Enter your gmail  account and test. If it works in the new User you know the problem exists in your current User.
or
2) You can do this in your current user and it will also nuke all Mail settings.
1)  Go to your User's Library folder. (if you don't know how to find, see this link.) Do steps a,b,c
a) Scroll to Mail folder.
Rename Mail OLD. [When you open Mail it will create a new Mail folder. You can revert to this folder if needed by removing OLD from the name. You would need to rename the "new" Mail folder first.]
b)  Go to Containers in the User's Library folder.
Delete the com.apple.mail folder.
c)  Go to Preferences in the User's Library folder.
If you find any com.apple.mail.plist files, delete these.
2) Log out under the Apple in the Menu bar. Log in.
3) System Preferences > Internet Accounts > Delete all accounts.
4) Open Mail.
5) Enter one account at a time. Test to be sure you are connected before adding other accounts.
If you have Gmail, be sure you have the All Mail folder selected to sync. Workarounds we previously used no longer work in Mavericks. You might need to go into your Gmail Settings in your browser to make the necessary changes. See this article for help:
Use Gmail with Mavericks Mail