Apple Mail Slow to Populate

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.