I have a Google Mail account but do not find the GMail app for iOS particularly appealing. Recently I heard of a new app, Twobird, from the makers of Notability which seemed interesting to me for two reasons;
1. You can set reminders to jog your memory to action any particular email, and
2. You can attach notes to an email that you refer to later when you can no longer remember what you had thought about the email content.
There are quite a few other additions to the app that may be worthwhile. As this is a new app, at version 1.0.1 as I write, it has quite a few rough edges, but the two features above gave me enough interest to give it a go.
The app is free and you can read more at:
https://www.twobird.com/I have no interest in the developer other than as a user of the Notability app, which like Twobird operates across multiple OS environments.