Why can’t Apple Mac Mail zoom/magnify when composing an email?

pjstarich wrote: I have to increase the font size to 16 or 18. Then I end up sending the email with crazy large font.

That should not happen if you increase the font size by using Mail > Preferences > Fonts and Colors > Message Font. You will see the larger size but thr recipient will not.

pjstarich wrote:

My default font size (12) appears nearly microscopic when composing an email on my Macbook. In order to read the email I’m composing, I have to increase the font size to 16 or 18. Then I end up sending the email with crazy large font. Command+/command- zoom in/out on an email I have received and most other windows, but not an email I’m composing. It appears to be a flaw that’s been around for a while in MacOS Monterey, Ventura, and Sonoma.

If one believes it is a Flaw, be proactive.

Then have a few suggestions ;

Start now and open an Apple Support Ticket as they are PAID  Apple Employees to deal will these types of issues . 

 Product Feedback - Apple and make it known to Apple regarding this ongoing issue 

At the same time, ask them to rewrite the previously mentioned versions of macOS

FYI - regardless of how small or how large the Font used when composing an e-mail

The Recipients email Client will render it differently from how it was formatted by the sender