mailcow
mailcow: dockerized is an open source groupware/email suite based on Docker.
mailcow relies on many well known and long used components, which in combination result in an all around carefree email server.
Each container represents a single application, connected in a bridged network.
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Horde
Horde is the most flexible groupware on the planet, and that makes it the perfect platform on which to build your business productivity software. Horde connects to (and officially supports) more backends (all the leading SQL, LDAP, IMAP, Sieve, SMTP, cache platforms available today) than any other open source groupware system. This means you can continue to use your existing userbase and your users do not have to remember any additional passwords. Horde's feature set rivals the largest enterprise email systems. We have an incredible feature set that compares favorably against any competition in our primary apps (mail, calendar, address book), and even more in our secondary apps (time tracking, wiki, ticketing, and more).
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FTGate
FTGate is an award winning Email, Groupware and Productivity server. With low installation and operating costs, secure communications and simple administration, FTGate offers our customers a powerful and cost-effective alternative to Microsoft Exchange. FTGate users benefit from extensive mail client support across multiple platforms, enabling users to choose their favourite mail client, and the powerful FTGate Web Mail client provides comprehensive email, groupware and productivity tools in an intuitive browser interface. Low hardware requirements combined with simple and quick Administration makes FTGate the best solution for your email, groupware and productivity needs. The workplace is now one in which everyone has their favourite device, so FTGate allows your users to choose their preferred devices, both mobile and desktop, and which platforms they work on.
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Mailu
Mailu is a simple yet full-featured mail server as a set of Docker images. It is free software (both as in free beer & as in free speech), open to suggestions and external contributions. The project aims at providing people with an easily setup, easily maintained and full-featured mail server while not shipping proprietary software nor unrelated features often found in popular groupware.
Main features include:
Standard email server, IMAP and IMAP+, SMTP and Submission with autoconfiguration profiles for clients
Advanced email features, aliases, domain aliases, custom routing
Web access, multiple Webmails and administration interface
User features, aliases, auto-reply, auto-forward, fetched accounts
Admin features, global admins, announcements, per-domain delegation, quotas
Security, enforced TLS, DANE, MTA-STS, Letsencrypt!, outgoing DKIM, anti-virus scanner, Snuffleupagus, block malicious attachments
Antispam, auto-learn, greylisting, DMARC& SPF, anti-spoofing
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