No direct Outlook Catch Up replacements listed yet
Open-source email clients & servers. To compare with Outlook Catch Up.
29 open-source email clients & servers
docker-mailserver
Email Clients & Servers
Production-ready fullstack but simple mail server (SMTP, IMAP, LDAP, Antispam, Antivirus,
MITvs Gmail★ 19k
Mailspring
Email Clients & Servers
:love_letter: A beautiful, fast and fully open source mail client for Mac, Windows and Lin
GPL-3.0vs Microsoft Outlook★ 18k
Mail-in-a-Box
Email Clients & Servers
Mail-in-a-Box helps individuals take back control of their email by defining a one-click,
CC0-1.0vs Gmail★ 15k
Stalwart
Email Clients & Servers
All-in-one Mail & Collaboration server. Secure, scalable and fluent in every protocol (IMA
OSSvs Google Workspace★ 15k
Thunderbird for Android
Email Clients & Servers
Thunderbird for Android – Open Source Email App for Android (fka K-9 Mail)
Apache-2.0vs Gmail★ 14k
Mailcow
Email Clients & Servers
mailcow: dockerized - 🐮 + 🐋 = 💕
GPL-3.0vs Google Workspace★ 14k
Inbox Zero
Email Clients & Servers
The world's best AI personal assistant for email. Open source app to help you reach inbox
OSSvs Superhuman★ 12k
Tuta
Email Clients & Servers
Tuta is an email service with a strong focus on security and privacy that lets you encrypt
GPL-3.0vs Gmail★ 8k
Mailu
Email Clients & Servers
Insular email distribution - mail server as Docker images
OSSvs Gmail★ 7.5k
Roundcube
Email Clients & Servers
The Roundcube Webmail suite
GPL-3.0vs Gmail★ 7.2k
SimpleLogin
Email Clients & Servers
The SimpleLogin back-end and web app
AGPL-3.0vs ImprovMX★ 7kMaddy
Email Clients & Servers
✉️ Composable all-in-one mail server.
GPL-3.0vs Gmail★ 6.1kMox
Email Clients & Servers
modern full-featured open source secure mail server for low-maintenance self-hosted email
MITvs Gmail★ 5.9k
Proton
Email Clients & Servers
Monorepo hosting the proton web clients
GPL-3.0vs Gmail★ 5.6k
FairEmail
Email Clients & Servers
Fully featured, open source, privacy friendly email app for Android
GPL-3.0vs Gmail★ 4.7k
Modoboa
Email Clients & Servers
Mail hosting made simple
ISCvs Google Workspace★ 3.5k
AliasVault
Password Management
Privacy-first password manager with built-in email aliasing. Fully encrypted and self-host
AGPL-3.0vs NordPass★ 3.2k
BillionMail
Email Marketing
BillionMail gives you open-source MailServer, NewsLetter, Email Marketing — fully self-ho
AGPL-3.0vs Mailchimp★ 16k
Rspamd
Email Clients & Servers
Rapid spam filtering system.
OSSvs Mimecast★ 2.5k
SOGo
Email Clients & Servers
SOGo is a very fast and scalable modern collaboration suite (groupware). It offers calenda
GPL-2.0vs Google Workspace★ 2.2k
addy.io
Email Clients & Servers
Anonymous email forwarding
AGPL-3.0vs ImprovMX★ 4.9k
Mail0
Email Clients & Servers
Experience email the way you want with Mail0 – the first open source email app that puts y
MITvs Superhuman★ 11k
Forward Email
Email Clients & Servers
Privacy-focused encrypted email for everyone. All-in-one alternative to Gmail + Mailchimp
OSSvs Fastmail★ 1.7k
Proton Mail Bridge
Email Clients & Servers
Proton Mail Bridge application
GPL-3.0★ 1.6k
Dovecot
Email Clients & Servers
Dovecot mail server
OSS★ 1.3k
RustMailer
Email Clients & Servers
A self-hosted Email Middleware for IMAP, SMTP, Gmail API, Graph API — built for developers
OSSvs Nylas★ 513
UnInbox
Email Clients & Servers
Modern email for teams and professionals. A replacement for outdated email technology and
OSSvs HEY★ 1.8k
Thunderbird
Email Clients & Servers
EXPERIMENTAL - copy of comm-central for forking on github
OSSvs Microsoft Outlook★ 195
Mailpile
Email Clients & Servers
A free & open modern, fast email client with user-friendly encryption and privacy features
OSSvs Spark Mail★ 8.8k
See every email client or server or the Outlook Catch Up listing.