what can you use besides an app to get your mail on iPhone?

A web browser? Aside for a few apps that provide significant advantages over the web version (or those that force you to use the app even in "requst desktop version" mode), I use a browser for everything. Hell, even though the YouTube app was preinstalled on my phone, I still used the mobile site because I just found the experience better.

a browser is an app... but I try to do like you and avoid random and single-purpose apps because they are riskier.

Exactly, I consciously check email when I want/need. So I don't even need push notification.