Why is my email all caps?

I suppose you are using rich text e-mail, then; even so, I find it odd that such a thing would happen automatically.

If you switch to plain text, do you still see it in all caps? Probably not, but test:

Mail->Preferences->Composing->Message Format: Plain Text

What font is selected for your text in Mail->Preferences->Fonts & Colors? Does changing it make any difference?

Did you try pressing the caps lock key to disable all caps?

Why to I feel I saw the Exact Same Question presented March 21, 2023 yesterday ?

Checking the CAP Lock on keyboard is stuck and will not unstick sounds like a reasonable question

Internal Keyboard ??

External Keyboard ?

What actions has the er already attempted to fix this issue ?

Reliable , accurate, details / context will really help to pinpoint a possible solution.

After all, we do not what to offer that which has already been attempted by the User 

J in Miami wrote:

There is invisible markup code that randomly turns my email text to all caps when I type. I'm asking if anyone knows what causes it, how to find the code, and disable it. AppleMail 16.0, OS13.2.1

Not with my Ventura installs there isn't.

P. Phillips wrote:

Why to I feel I saw the Exact Same Question presented March 21, 2023 yesterday ?

Maybe because it was posted yesterday?