I’ve been doing PC hardware for over 25 years. This is likely related to your laptop display - either the cable connecting the panel to the motherboard, the panel itself, or some motherboard component connected to the display output that has failed.

Try pivoting the display back and forth and see if the glitches change in response. If they do, it’s the cable.

Beyond that, you’d need to do some testing to find the hardware component that has gone bad.

About a year ago, I trialed both Proton Mail and Tuta mail. Proton mail worked out better for my needs, but YMMV. 

One nice thing about switching providers is that it gives you the opportunity to rid yourself of years of built-up cruft and spam.