Open Source Email
Email clients that are open source, allowing users and developers to modify and customize the source code.
Updated June 14, 2026
Products that define this theme
A representative set of Email Client Software products that exemplify Open Source Email, curated as a starting point for finding similar software.
Selected from G2's verified user reviews and ratings, then matched to this theme for relevance.
How Did G2 Choose These Open Source Email Products?
The 3 products shown represent a defining sample for the "Open Source Email" theme within Email Client Software on G2 — not an exhaustive list. They are a curated starting point for discovering similar software.
- Sourced from products with verified G2 user reviews and ratings.
- Matched to this theme based on each product's described capabilities and fit, ordered by relevance.
- Rankings and inclusion are unbiased and are not influenced by vendor payment.
Refreshed weekly. Last updated: June 14, 2026.
Thunderbird is a free, open-source email client developed by Mozilla, designed to provide users with a secure, customizable, and efficient email management experience. Compatible with Windows,...
Zimbra Desktop is a free and open source email client application that gives you online and offline access to all your email accounts in one place. Zimbra Desktop works with many types of email...
K-9 is an opensource email client based on the Email application shipped with the initial release of Android. K-9 is focused on making it easy to chew through large volumes of email.