Can just opening email infect Mac in any way? I'd like opinion on this:

If I open email and see text, can it infect my Mac? Not opening attachments, just email itself. Can that be dangerous? I delete all suspicious and unknown ones, but there are few where I can't be sure or have to see the insides.

I have no real time scanner and sometimes run Malwarebytes.
Can it be dangerous? Absolutely it can, there might be an unpatched vulnerability in the Mail app. But no one can tell you if such a vulnerability actually exists, because if it was known then it would already have been patched.