SophiMail is described as 'fully-featured email and collaboration server solving the most critical email issues: maximizes Privacy, Portability and Cost efficiency, Admin & User productivity. Ideal for private hosting on VM: on cloud, on premises or hybrid' and is a Mail Server in the Office & Productivity category. There are more than 25 alternatives to SophiMail for a variety of platforms, including Linux, Windows, Online / Web-based, Self-Hosted solutions and Mac. Most alternatives are Mail Servers, WebMail Providers and Calendars. The best alternative is Google Workspace. It's not free, so if you're looking for a free alternative, you could try mailcow: dockerized or Zimbra Collaboration Suite. Other great apps like SophiMail are Zentyal (Paid, Open Source), Kopano (Freemium, Open Source), SOGo (Freemium, Open Source) and hMail Server (Free, Open Source).
Zentyal is a native Microsoft Active Directory implementation on Linux incorporating all the network services required in a small and medium business environment: Directory & Domain Server, Mail Server, Gateway and Infrastructure Server.
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.
A fully fledged, free email server solution, an open source project (GPL v2). Use official binary packages from Linux/BSD distributions, with both i386 and x86_64 support. Easy, fast deployment in LESS THAN 1 MINUTE. View YouTube Video to check how easy it is.