If you want to migrate Zimbra to Exchange Server then I suggest third-party software like KDETools Zimbra to Exchange Server Migration tool. The software allows the user to check the preview of emails with attachment and header details. The application directly migrates Zimbra mail to Exchange server and Office 365 account. The software migrates Zimbra to Several file formats such as PST, MBOX, EML, EMLX, HTML, PDF, NSF, OLM, and etc. This software has no file size limitation to migrate an oversized Zimbra file to Exchange Server.