Mail.app Preferences takes 3 minutes to load

LuigiBenetton wrote:

When I choose Preferences form the Mail menu in Mail.app, the dialog takes 3 minutes to load. I have reported this bug to Apple, but I'm hoping other people have successfully solved this issue.

If I close the dialog (not the app) and choose Preferences again, the dialog loads normally.

This has been an issue since I updated my Mac to Catalina. It did not occur before this.

In a possibly related issue, Spotlight is a little slower than it was in Mojave, though the issue is not as bad.

One way to sort these one off anomalies like yours is to reinstall the combo update on top of your existing macOS 10.15.5

Combo update macOS 10.15.5 https://support.apple.com/kb/DL2040?locale=en_US

LuigiBenetton wrote:

Regrettably this combo update did not solve the issue. Mac Mail Preferences still takes 3+ minutes to appear, during which Mac Mail hangs

Ok LuigiBenetton, thanks for the report, I'll see if we can get to the bottom of this.

Here is your next task in an effort to resolve the issue:

Quit mail.

From the Finder>Go>Go to Folder, copy & Paste:

 ~/Library/Containers/com.apple.mail

Highlight all the contents in this folder. Place your mouse on the selection,

Then Control click (right-click) and choose "New Folder with Selection”. Do not move the new folder from this current location.

You can close the Finder window.

The next step will be to restart the Mac and test

After the computer is restarted, open the Mail.app> Preferences to see if it opens properly.

ref: step by step including pics:

https://discussions.apple.com/thread/251147316?answerId=252188310022#252188310022

LuigiBenetton wrote:

I've downloaded the file and plan to run it when I leave the office for the day.

Question: is this like other updates that you can just leave to run on their own?

I never leave an update or upgrade to run on its own.

So don't know what to tell you— try it and see.