JMAP is an alternative protocol to IMAP while EmailEngine is basically a proxy. If you want to build a new Outlook or Thunderbird you probably have to connect t

JMAP is an alternative protocol to IMAP while EmailEngine is basically a proxy. If you want to build a new Outlook or Thunderbird you probably have to connect to email servers directly and speak IMAP or JMAP. If you want to easily integrate a lot of email accounts with your existing system and only care about basic info (like notifications about new emails etc) then EmailEngine is easier to use as it handles all the hard work itself.