OSX Mail App Corrupt - OS Reinstall?

[mcdhu]

I am running a late 2009 iMac with OS High Sierra 10.13.6 as the latest it will update to.
I use AOL mail via the OS mail application - version 11.5 (3445.9.7). Unfortunately, this has become corrupted and try as I might, I have been unable to restore the various IMAP and SMTP settings within the app. I am not confident enough to do a fresh instal of the whole OS and am therefore currently using AOL webmail which works ok but I would like to continue to use the OS mail app as I have done for years.
I have a Western Digital 'My Passport Studio' permanently plugged into the iMac but have never has to restore anything from it.
My question, therefore, is: 'can I somehow reinstall the OS Mail App alone from a backup in 'My Passport/Time Machine' or would I have to completely reinstall the OS to get the OS Mail app back to its former glory?'

[Jhieminga]

I am trying to understand what it is that has become corrupted? If it's just the settings that have been messed up, AOL helpdesk or an online page from AOL should be available to help you get those back. That's just a matter of entering the correct server settings. As you're using IMAP, you should not need to restore anything, all your folders are still available on the server.

There is an explanation here on how to retrieve locally stored folders using Time Machine, but I suspect that this is not what you need: https://www.macworld.com/article/231354/how-to-recover-a-mail-folder-from-time-machine-in-macos.html If you restore a folder this way, your settings for the account would still prevent you using the Apple Mail functions on your AOL e-mail.

First, have a look here and note the IMAP settings: https://help.aol.com/articles/how-do-i-use-other-email-applications-to-send-and-receive-my-aol-mail I guess Apple Mail is not a commonly used Mail program in AOLs eyes as they do not provide any explanation for that.
There is an extensive explanation on how to set up AOL in Apple Mail here: https://www.lifewire.com/access-your-aol-email-using-apple-mail-2260068
I would suggest removing existing AOL settings by selecting 'Mail' - 'Accounts' from within the Mail app, and removing the line that corresponds to your AOL mailbox (select and click on the minus sign at the bottom). Do this first, then follow the steps above to add a new account.

[mcdhu]

Thanks for your time and thoughts, Jhieminga. I'll have a look as you suggest.

mcdhu

[awair]

You do not need to re-install the whole OS. Although that is Apple's official solution if it really has become totally corrupted, it is unnecessary and dangerous.

If it is only settings, then deleting a couple of 'plist' files will present a 'fresh' setup.

If the app itself is corrupted (unlikely), there is a tool you can use to selectively replace macOS or app files.

It’s available for a free trial. I've used it a couple of times, but watch the YouTube videos to double-check the steps…

Pacifist
https://www.charlessoft.com

Good luck.

[mcdhu]

Thanks Awair, that's encouraging.
Cheers
mcdhu