GooBook allows to use Google Contacts from
the command-line and from MUAs such as mutt.

Lieer is a fast email-fetching, sending,
and two-way tag synchronization between notmuch and GMail.

This program can pull, and send, email and labels (and changes to labels)
from your GMail account and store them locally in a maildir with the labels
synchronized with a notmuch database.
The changes to tags in the notmuch database may be pushed back remotely to
the GMail account.

• Lieer @ GitHub.

A Command-Line Utility to automatically backup Google Mail, Calendar & Contacts to local files.

This module automatically downloads your Google Mail, Contacts & Calendar to separate files. It'll sync only new Mails, Contacts & Events.

Free to host and open-source cal.com / calendly alternative built on Google-Apps-Script for Gmail users. Built with modern technologies like React, TypeScript, Shadcn/UI, and Vite.

• Someday @ GitHub.

PEPS is an email, file sharing and collaboration server that intends to fullfil the need for high-quality on-premises software that could rival with top-notch SaaS products such as Gmail or Dropbox, and innovate with new features.