If you are having problems with the external keyboard on iOS 15 when you are editing an email then you can change the system setting. Open the Apple Settings app. Then open Accessibility - Keyboards and turn off "Full Keyboard Access"

If you are using an external keyboard for your device, you can use the built in following key commands inside AltaMail:

esc   Cancel a popup dialog or go back to the previous screen
enter   Same as the OK button on a popup dialog
⌘ n   New email
⌘ ←   Display the previous email (when viewing an email)
⌘ →   Display the next email
⌘ backspace   Delete an email
⌘ f   Show the search field
⌘ u   Undo the last action when the undo bar is showing
⌘ r   Reply to an email
⌘ shift r   Forward an email
⌘ enter   Send an email
⌘ p   Print
⌘ a   Select All emails in a list
⌘ s   Save an email as a file