How to change default mail program

First find out the reason why mail is slow you can use etrecheck and post the results , unwanted softwares , anti virus , apps installed are the major cause .

You can delete the mail application by entering in system preferences > internet account .

Select the account and click on subtract sign , the mail account will be deleted and if click on mail there are no mails in it .

But still all are saved on the server , click on mail on top menu bar > click on add mail and select the mail account and you have to click on continue , type the web mail address > next then type the web mail password and click on done to save .

Open mail app click on get new mail messages in all accounts icon .

The mails will start downloading if it is laptop plug the charger and let the mail application be opened for hour or two until all mails get downloaded .

High network speed always helps .

Mickey Faigen wrote:

The native Mail program is buggy. Need to change the default.

Don't launch Mail.app

Simply open, setup and use the alternative mail client of your choice. Open mail.app just one last time to set the Default in the Preferences>General

Do a backup, preferably 2 on 2 separate drives.

Quit Mail.

Go to Finder and select your user/home folder. With that Finder window as the front window, either select Finder/View/Show View options or go command - J. When the View options opens, check ’Show Library Folder’. That should make your user library folder visible in your user/home folder. Go to Library/Containers/com.apple.mail. Move the folder com.apple.mail to your desktop. You must move the entire folder, not just the contents.

Restart, re-launch Mail and test. If the problem is solved, recreate any required Mail settings and import any emails you want to save from the folder on the desktop. You can then put the folder in the Trash. If the problem remains, return the folder to where you got it replacing the one that is there.

If that doesn’t solve it repeat the above using Containers/com.apple.MailServiceAgent.

Information learned from Linc Davis. Thanks to leonie for some information contained in this.

Mail crashing

Crashes/quits unexpectedly

See this article Mail General preferences on Mac - Apple Support

So , you can't change this settings , for other mail accounts , you have to create a new web mail account for that service like yahoo , outlook ...etc .

You can't mix up two accounts as individual server is secured and confined .

I'd have a look at what's going on with the system and particularly with mail; at what's happing and making it buggy.

The trigger here might be a corruption in a mail configuration file, a problem within mail itself, something weird with the mail server(s) involved, a hardware or network problem, insufficient system memory for current requirements, or a problem such as those that can be caused by anti-virus or anti-malware tools, or by some other software that might be resident on this Mac.

One helpful tool here is Etrecheck, and you can download and run that and then cut-and-paste a copy of the report here. From that, we can get a better idea of the configuration and its details.

Mickey Faigen wrote:

It might have something to do with an anti-virus program that finds trouble seemingly everywhere.

Might? Add-on anti-malware tools are quite common sources of weirdness and instability for macOS users. As a test, remove the anti-malware tool per the vendor's instructions, reboot, and try again.

I would carry forward. Maybe the new mail client will have the default option setting as well.

There is no stand alone mac Mail.app program. Reinstalling the macOS on top of your existing macOS is the only way to get a renewed copy of the app.

See if the instructions help in this support article > Set the default email app or web browser on your Mac - Apple Support

Download, run, and post the entire report of Etrecheck.