Syncing Emails
How do I get my IPhone 13 to sync with my 10th generation apple IPad?
iPad, iPadOS 16
if they use the same appleid then apples icloud mails should be in sync on them
if it's another mail provider then just add the mail account in settings, of cause if it's a mail provider that use the old pop3 type they can't really be in sync
The Top 4 Differences Between IMAP and POP3 | Spiceworks - Spiceworks