What are some alternatives?
G Suite - Google's encompassing suite of cloud-based business apps.
iRedMail - A fully fledged, free email server solution, an open source project (GPL v2).
Zoho - Zoho is an all-in-one online office suite.
Microsoft Exchange Server - Microsoft Exchange Server is a messaging and collaborative software product developed by Microsoft.
Slack - A messaging app for teams who see through the Earth!
LibreOffice - Free office suite, open source, and compatible with .doc, .docx, .xls, .xlsx, .ppt, .pptx files. Updated regularly – download for free. Originally based on OpenOffice.org.