iCloud Mail. I have a Proton account, but the app takes several seconds to load and show me my messages on my phone and I hate the delay. Plus, as of iOS 17, Mail now autofills email verification codes and delete the email afterwards. Plus Mail is built into Siri and all that jazz, so it sometimes shows possible events that I can add to the calendar. So convenient.
1:46157.75 using mobileSafari on iOS with NextDNS.