Apple Mail is VERY Slow and gone wonky!

[Raven]

I posted a previous question that my 1 TB HD was almost full with only 18GB space left. Still trying to figure that out. Now, I'm having problems with Apple Mail. Not sure if my full HD is the problem, or what is going on...
- From a RESTART, Mail app takes 12 minutes to be on my screen and all emails show up.
- Cursor moves very slowly, and I have to key in slowly to wait for the text to catch up.
- When RESTARTING, I get "Mail interrupted restart. Quit Mail and restart". Have to shut off with Power Button. I had to FORCE QUIT the Finder cause it takes so long.
- When I tried to send an email with attachment - "Could not save info about mailboxes. Not enough empty space on Home Folder".

Do I need to rebuild Mailbox as a solution? If so, which one - mail accounts (Yahoo)? InBox? Drafts? Flagged? Work? etc I'm using my MBP as a back up for emails and browsing, but i can't get access to all my files on my iMac which is a problem right now!

[Raven]

Well, my Apple Mail works fine on my MBP and iPhone. So, it's an iMac problem only?
I just rebooted my iMac and ALL my mail was gone from several accounts - ISP, Yahoo, Gmail!!
When I tried to start my old Mail account and enter my password it tells me the "account already exists."
When I restarted again, my Mail came back up! BUT in a few moments, I get this message again...
"Mail cannot save information about your mailboxes because there is not enough space in your Home Folder". Have to Quit.
Damn frustrating. Spending hours trying to fix this. Any good advice will be super appreciated! 

[Raven]

Yesterday I rebooted because my MAIL was frozen & everything was super slow. All my mail accounts disappeared (yahoo, gmail, Apple). I started to enter each account again, but it would not accept my password!  After a while, I gave up. Today, all my email accounts are back and OK. Even typing is normal. Whew! But WTH is going on? Thoughts?

[krissel]

Suggest you remove as much as you can from your mail inboxes. Check the prefs for each account to see when items in the Trash are actually deleted. They may stay there for a month or forever depending on what you selected. Once you are sure you have truly deleted a bunch and you have emptied your Mac trash, then try rebuilding.


Empty as many caches as possible.
https://www.macworld.com/article/677632/how-to-delete-cache-on-a-mac.html



Also would boot to Recovery mode and run Disk First Aid. It may help with the directory that keeps track of files and folders.


https://support.apple.com/en-us/102611

[Raven]

Krissel,
Thank you again for all your advice.  Taking me a while to study all the cache info as I don't want to screw anything up. At least I've got my email working again and a bit of HD space.  I have another question related to that. Not sure if I should post that here or start another Topic? Seems like I'm hogging this forum with all my problems. The nearest Mac tech helper is 500 miles away. May have to take my iMac to him and get all this cleaned up.