Formatting is all over the place after I view my SENT item email(s) where I copied and pasted content in eM Client. In particular, Gmail. Fonts are all different sizes. When I look at my email within Gmail itself it appears fine.
I asked ChatGPT and the recommendation was to only compose email directly via the web based email client and avoid applications like eM Client.
Nonetheless, I never noticed this issue before upgrading to version 10 but it seems the issue may have been present as far back as 2016:
[Font size changes in sent email when viewed in gmail]