I have an Imac with Apple Mail 11.2
High Sierra 10.13.3 however it has had this issue for several versions of program updates.
I click to start the program, it appears on my screen however it does not start working or downloading mail for 1-4 minutes.
I keep most of my mail in separate folders.
12 accounts download, but only 2 are active. 9 are Gmail 3 apple.
OS X Yosemite (10.10.5), Same problem with last few versions
Try testing it in the Safe Mode.
Safe Mode - About El Capitan
also Sierra
Safe Mode Startup – El Capitan. also Sierra
If it works in the Safe Mode, try running this program when booted normally and then copy and paste the output in a reply. The program was created by Etresoft, a frequent contributor. Please use copy and paste as screen shots can be hard to read. Click “Share Report” button in the toolbar, select “Copy to Clipboard” and then paste into a reply. This will show what is running on your computer. No personal information is shown. You can run the report for free at least once, but if you run it several times, at some point it will ask you to pay a license fee.
12 accounts download, but only 2 are active. 9 are Gmail 3 apple.
Do you mean you have only 2 enabled or only 2 have activity?
This could be part of your issue. If all 12 are enabled, that is a lot of server connections to establish. There are 2 server connections for each of 12 accounts and they each need to log in to start sending/receiving mail.
I would suggest disabling all but one account to start and test as you enable them one by one to see if and when the response time(s) are affected.
Apple Mail Slow to Populate
