You can receive email from your email accounts on your Apple Watch.
Select email account
Tap the Digital Crown.
Tap the email icon.
Tap arrow left.
Tap the required email account.
Tap the required email.
Reply to email using voice input
Tap Add Message.
Reply to email using text input
Tap Add Message and key in the required text.
Reply to email using quick reply
Tap the required quick reply.
Return to the home screen
Tap the Digital Crown twice to return to the home screen.