Is backup of IMAP necessary when switching to a new Macbook I am switching to a new macbook and am in that case wondering, if it is necessary to backup my e-mail. All my mailboxes are Exchange or IMAP. I mean they are already located on the server, so is it even necessary to back up my mailboxes. Can't I just add the accounts on the new computer and they will sync automatically, leaving me at the same place as I was on my old Macbook?

Thanks in advance.
IMAP and Exchange both keep your email on the server.   Adding the account on a new computer will allow you to access your existing email on a new local machine.

While you didn't mention POP3 in your question, that would be the email protocol that was designed to store your messages locally.  IMAP and Exchange protocols came later.