Citadel Alternatives

Citadel is described as 'Is a collaboration suite (messaging and groupware). It is designed to run on open source operating systems such as Linux or BSD. In order to modernize the Citadel platform for the Internet, the Citadel/UX developers added functionality such as shared calendars, instant' and is a webmail provider in the office & productivity category. There are more than 10 alternatives to Citadel for a variety of platforms, including Web-based, Windows, Linux, Self-Hosted and Mac apps. The best Citadel alternative is Zimbra Collaboration Suite, which is both free and Open Source. Other great apps like Citadel are Kolab Community, hMail Server, OX App Suite and Microsoft Exchange Server.

Citadel alternatives are mainly Mail Servers but may also be WebMail Providers or Email Clients. Filter by these if you want a narrower list of alternatives or looking for a specific functionality of Citadel.

Citadel

Free • Open Source
WebMail Provider

Is a collaboration suite (messaging and groupware). It is designed to run on open source operating systems such as Linux...

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Citadel alternatives page was last updated

Zimbra Collaboration Suite
Is this is a good alternative?
Yes
No
Freemium • Open Source
Mail Server
Calendar App
Team Collaboration Tool
Linux
Online
Self-Hosted
41 Zimbra Collaboration Suite alternatives
Zimbra Collaboration is an open, secure collaboration tool for email, calendaring, tasks and more. With the most innovative web application available today, Zimbra boosts the productivity of users on any desktop and dramatically reduces TCO compared to legacy platform vendors.
- - Zimbra Collaboration Suite is the most popular Web-based, Linux & Self-Hosted alternative to Citadel.
- - Zimbra Collaboration Suite is the most popular Open Source & free alternative to Citadel.
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Zimbra Collaboration Suite Features
1. Real time collaborationMultiple users can work together in Zimbra Collaboration Suite simultaneously.
ActiveSync
Active Directory integration
Kolab Community
Is this is a good alternative?
Yes
No
Freemium • Open Source
Linux
Online
Self-Hosted
42 Kolab Community alternatives
Kolab is entirely Free and Open Source Software (a.k.a. FOSS), and uses Open Standards. We’ll get to why this is important to us, and hope that it is important to you thereafter.
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Kolab Community Features
1. Real time collaborationMultiple users can work together in Kolab Community simultaneously.
CalDAV Support
WebDAV Support
IMAP Support
CardDAV Support
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hMail Server
Is this is a good alternative?
Yes
No
Free • Open Source
Mail Server
Windows
23 hMail Server alternatives
hMailServer is a free e-mail server for Microsoft Windows. Its used by Internet service providers, companies, governments, schools and enthusiasts in all parts of the world.
- - hMail Server is the most popular Windows alternative to Citadel.
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hMail Server Features
IMAP Support
POP3 Support
SMTP Support
Convert images to PDF
Discontinued
hMail Server is no longer supported by the people who created it and has been discontinued – so use it at your own risk.
OX App Suite
Is this is a good alternative?
Yes
No
Free • Open Source
Mail Server
WebMail Provider
Calendar App
Linux
Online
Self-Hosted
Software as a Service (SaaS)
19 OX App Suite alternatives
The OX App Suite by Open-Xchange is web-based platform offering a suite of apps like an email client, calendar, contacts magement, cloud storage with synchronization and productivity apps for word processing, spreadsheets and presentations.
- - OX App Suite is the most popular SaaS alternative to Citadel.
Suggest and vote on features
OX App Suite Features
1. Real time collaborationMultiple users can work together in OX App Suite simultaneously.
2. Cloud SyncSync your data (notes, documents, bookmarks, etc.) across your different devices and to the cloud.
3. Calendar IntegrationOX App Suite lets you sync your tasks and events with your calendar application.
Personal Information Manager (PIM)
Group Mail
German
WebDAV Support
WebDAV Sync
Microsoft Exchange Server
Is this is a good alternative?
Yes
No
Paid • Proprietary
Mail Server
Windows
Online
44 Microsoft Exchange Server alternatives
Microsoft Exchange Server is a messaging and collaborative software product developed by Microsoft. It is part of the Microsoft Servers line of server products and is widely used by enterprises using Microsoft infrastructure solutions.
- - Microsoft Exchange Server is the most popular commercial alternative to Citadel.
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Microsoft Exchange Server Features
1. Real time collaborationMultiple users can work together in Microsoft Exchange Server simultaneously.
CrossBox
Is this is a good alternative?
Yes
No
Paid • Proprietary
Mail Server
WebMail Provider
Email Client
Online
Android
iPhone
Android Tablet
iPad
Self-Hosted
39 CrossBox alternatives
Real-time email, chat, audio/video calls & conferences, file-sharing, and contacts app with a modern and intuitive UI.
- - CrossBox is the most popular Android, iPhone, iPad & Android Tablet alternative to Citadel.
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CrossBox Features
File Hosting
MDaemon Messaging Server
Is this is a good alternative?
Yes
No
Paid • Proprietary
Mail Server
Windows
23 MDaemon Messaging Server alternatives
Low cost, easy to use Email Server software for virtual, on-premise, or hosted deployments for companies that want control of their email. Integrated web-mail with doc sharing, Drop Box integration, client and server side encryption.
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MDaemon Messaging Server Features
Encrypted Email
Outlook integration
IMAP Support
Dropbox integration
EGroupware
Is this is a good alternative?
Yes
No
Freemium • Open Source
Mail Server
Calendar App
Project Management Tool
Linux
Online
Self-Hosted
Software as a Service (SaaS)
24 EGroupware alternatives
Online Collaboration with Chat and Online Office. Is developed as open source software in Germany, offered as free community version and as commercial version. Operation as self-hosted or as SaaS from the computer centre.
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EGroupware Features
1. Real time collaborationMultiple users can work together in EGroupware simultaneously.
2. Kanban BoardEGroupware allows you to organize your workflow by moving cards with drag-and-drop functionality between multiple columns.
Document sharing
Remote Work
Web-Based
CalDAV Support
RDP
WebDAV Support
CardDAV Support
Calendar Sync
Customizable
Zarafa
Is this is a good alternative?
Yes
No
Paid • Proprietary
Mail Server
Calendar App
Mac
Windows
Linux
Online
15 Zarafa alternatives
Open Source Collaboration, providing integration with your existing Linux mailserver, native mobile phone support, Outlook "Look & Feel" webaccess and stable Outlook sharing (100% MAPI).
- - Zarafa is the most popular Mac alternative to Citadel.
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Zarafa Features
1. Real time collaborationMultiple users can work together in Zarafa simultaneously.
Discontinued
"Last year we released the announcement that Zarafa customers could transition to Kopano. We also announced that Zarafa would not be maintained beyond May 1st, 2017. Most ZCP customers have moved to a Kopano subscription now."
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Atmail Email Server
Is this is a good alternative?
Yes
No
Paid • Proprietary
Email Client
WebMail Provider
Mail Server
Linux
Online
67 Atmail Email Server alternatives
Atmail webmail system offers a webmail client, email server platform and mailserver appliance for Linux, Unix and Windows.
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Atmail Email Server Features
Group Mail
iMail
Is this is a good alternative?
Yes
No
Paid • Proprietary
Mail Server
WebMail Provider
Windows
Self-Hosted
42 iMail alternatives
Fast, safe, heavy mail solution. Web-client access, LAN or WAN self-hosted server, maintenance-free design. No Windows server and database server required, unlimited mail accounts, storage, attachment size, custom logo. Free for commercial use.
iMail has no features, suggest some!
Expanding Communication
Is this is a good alternative?
Yes
No
Paid • Proprietary
Mail Server
Email Client
Linux
34 Expanding Communication alternatives
Turnkey Solutions for the Enterprise Cloud

Installation, Configuration, and Management tools for enterprise email, collaboration, messaging, video conferencing, file sharing, and file transfers.
Suggest and vote on features
Expanding Communication Features
1. Cloud SyncSync your data (notes, documents, bookmarks, etc.) across your different devices and to the cloud.
Contacts
CalDAV Support
Cloud based
Video Conferencing
CardDAV Support