You can reply to or forward emails in the Mail app.
In the sender’s message, touch and hold the first word of the text, then drag to the last word. (See on your iPhone.
Tap in the message, tap Set up an automatic reply in Mail on iCloud.com.
If you have any iPhone 16 model, iPhone 15 Pro, or iPhone 15 Pro Max, Apple Intelligence can suggest a reply to email you receive. See Save a draft in Mail on iPhone