Comment by vel0city

I am using New Outlook.

I don't doubt it's happening to you, but I've never experienced it. And I'm not exactly using bleeding edge hardware here. A several year old i5 and a Ryzen 3 3200U (a cheap 2019 processor in a cheap Walmart laptop).

Maybe your IT team has something scanning every email on open. I don't know what to tell you, but it's not the experience out of the box on any machine I've used.