The best paid alternative to Microsoft Exchange is Google Workspace. If that doesn't suit you, our users have ranked more than 25 alternatives to Microsoft Exchange and many of them is paid so hopefully you can find a suitable replacement. Other interesting paid alternatives to Microsoft Exchange are Kopano, Zimbra Collaboration Suite, Axigen and SmarterMail Mail Server.
Google Workspace delivers a cloud-based suite combining Gmail, Calendar, Meet & Drive to enhance collaboration through tools like Docs and Sheets. Offers secure storage options, custom domain emails, and robust management capabilities with 2FA and 24/7 support.
Kopano puts an email, video meetings, calendaring, and file sharing solution within one single interface.
Stable and cheap backend, flexible frontend support, open source, in full control of your data
Scalable, open source with a great UX and it has all the features I need
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.
Axigen provides a multi-tenant, fully integrated, multi-platform, all-in-one email, calendaring and collaboration messaging solution. It grants extensive branding options and is localized in over 29 languages (including right-to-left writing mode).
Axigen is so much easier to use, it has the on-premise solution, and has unbeatable prices!
SmarterMail is the only other email server on the market with native support for MAPI, the protocol that powers Exchange and Outlook. That means anything you can do on Exchange you can do with SmarterMail: no plug-ins and no additional software required.
Offers native MAPI integration, along with EWS and EAS. Works great with Outlook, but also other clients like the MacOS client, eM Client, and others. No CALs, like for on-prem Exchange.
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.
Open Source Collaboration, providing integration with your existing Linux mailserver, native mobile phone support, Outlook "Look & Feel" webaccess and stable Outlook sharing (100% MAPI).
Real-time email, chat, audio/video calls & conferences, file-sharing, and contacts app with a modern and intuitive UI.
Atmail webmail system offers a webmail client, email server platform and mailserver appliance for Linux, Unix and Windows.
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.
Sanwhole Exchange is a server running iMail, iPress and iStore services. iMail is an enterprise-class email server does Microsoft Exchange and Gmail work. iPress sets blog, forums and tickets in one. iStore is an online store.
Turnkey Solutions for the Enterprise Cloud
Installation, Configuration, and Management tools for enterprise email, collaboration, messaging, video conferencing, file sharing, and file transfers.
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Free and open source, and has most of the things you want from Exchange, including shared calendars.