apple mail running fans like crazy on my macbook pro 2018

I have a 15in 2018 macbook pro.

when I start mail my machine starts the fans up at full tilt. the CPUs fluctuate from 50ºC to 100ºC and the process % is up to around 130% sometimes. (the temperature of my machine is never below 50ºC...)

I have turned it off and on again (app, computer, network, you name it)

If I turn off mail the trouble goes away.

I have reset the SMC

I have reset the PRam

I have an exchange account on there but turning it off does nothing different

Everything else is IMAP

I turned all the calendars off and removed the calendar plist and the calendar folder in the library

I have limited the # of items in mail to 100

I if the temp goes down and the fans turn off (right now for instance) because I'm not in mail for a while, and I switch to mail and click on to look at a message, the fans jack back up immediately. I have HIGH intensity CPU hog applications that don't affect the machine this way...

I've removed every startup proc there is.

But the truth is nothing bad happens unless I'm in mail. so startup procs are not to blame.

Any help would be appreciated.

Thanks