You can switch AltaMail to Dark Mode for viewing emails with less glare at night.

Dark Mode in AltaMail will work on previous iOS versions, not just iOS 13. You can choose Dark Mode inside AltaMail by opening the App Settings and then open the "Email Appearance" section (View).

Tap on the Dark Mode heading to view the options screen. You can choose to use the Default option which will use your device settings.

You can also choose Light Mode or Dark Mode which will override your device settings just for AltaMail

You can also tap on the Schedule option to choose the times and days when you want to switch to Dark Mode. AltaMail will then automatically switch to Dark Mode with the schedule. This is separate from the iOS 13 schedule.

When you are viewing an email in Dark Mode, you can change the email content to Light Mode in the email action menu. (Button with arrow and square). This will change the viewing mode for the current email and remember the Light Mode setting for next time.

If you switch to Dark Mode the Email Appearance settings will be different. When you edit settings while using Dark Mode those settings are only used for Dark Mode. Switching to Light Mode will use a different set of Email Appearance settings. Email Appearance