Instructions
There are multiple ways to reply to an email message in the Mail app on your iPhone or iPad.
Jump to: Method B: From within the message
Method A: From your messages list
A1) Long press on the message to which you wish to reply.
A2) Tap Reply or Reply All.
A3) Type your reply text and make any other desired changes to the outgoing message. In the top right-hand corner, tap the send icon (upward-pointing arrow).
Method B: From within the message
B1) At the bottom of the message, tap the Reply button.
B2) Tap Reply or Reply All.
B3) Type your reply text and make any other desired changes to the outgoing message. In the top right-hand corner, tap the send icon (upward-pointing arrow).
Outcome
You have sent your reply to the email message.