Mail runs constantly

Judson Leonard wrote:

You don't understand. The activity window shows when a check occurs. I understand that, and it's not frequent. Mail is running continuously even when not checking for incoming mail.

To trouble shoot further you can:

—Try a SafeBoot https://support.apple.com/en-us/HT201262

Takes noticeable longer to get to the login screen, does a 5-15 minute disk repair before it fully boots up, and certain system caches get cleared and rebuilt, including dynamic loader cache, etc.

Login and test. Reboot as normal and test as caches get rebuilt.

In Safe mode third party system modifications and system accelerations are disabled, it removes malware, etc hampering smooth operation, however a reboot will put it back to normal mode.

This test will tell you if third party interference; extensions etc are not loaded in safe boot mode.

Mail Preferences > General panel, and assess the check for new messages frequency

Mail fetches your email and you can set the duration.

Does one have several e-mail accounts with different servers ie iCloud, gmail, outlook