email

Usual contents-migration path:

Transfer data from your previous iOS or iPadOS device to your new iPhone, iPad, or iPod touch - Apple Support

if the usual contents migration was not performed and this iPhone was set up new, then add the mail accounts manually. You’ll need the same setup details for your mail provider as would be used from the previous setup.

If the usual contents migration was not performed, the needed contents from mail that was downloaded locally to the previous iPhone will have to be either uploaded back to the mail server, and re-downloaded to the new iPhone from there, or discarded

Hello there!

If you were using your "@icloud.com" email account, the mail should have automatically synced. I'm guessing that you're using another email. To add that email and transfer the mails you go into the Settings app -> Email -> >Accounts -> Add account. Here you can add the email that you were using on your old phone and the mails should synchronize instantly after you have added the email.

Feel free to reply if you have any further questions.

// Gustav