Imapsync

Install ImapSync Tool on Ubuntu Bionic/Xenial & Sync GMail to Zimbra

Install ImapSync Tool on Ubuntu Bionic/Xenial

https://github.com/imapsync/imapsync/blob/master/INSTALL.d/INSTALL.Ubuntu.txt

Allow IMAP

https://mail.google.com/mail/u/0/#settings/fwdandpop

Disable Two Factor Auth & and allow less secure apps temporarily

https://myaccount.google.com/lesssecureapps

Other

You may want to change settings like conversation mode

https://github.com/imapsync/imapsync/blob/master/FAQ.d/FAQ.Gmail.txt

Gmail to Zimbra sync example

imapsync \

          --user1 jeremy@example.org \
          --password1 <YOURPASS> \
          --host1 imap.gmail.com \
          --gmail1 \
          --ssl1 \
          --user2 busk@example.io \
          --password2 <YOURPASS> \
          --host2 zmail1.example.io \
          --ssl2

Python Wrapper

A little rough but an example wrapper. Probably would write my own.

https://gist.github.com/antoine-briand/636ba063be1d24ab0a9d