What are some alternatives?
When comparing Zimbra Collaboration Suite and iRedMail, you can also consider the following products
Microsoft Exchange Server - Microsoft Exchange Server is a messaging and collaborative software product developed by Microsoft.
Roundcube - Web-based IMAP email client
G Suite - Google's encompassing suite of cloud-based business apps.
Thunderbird - Thunderbird is a free email application that's easy to set up and customize - and it's loaded with great features!
Zoho One - Zoho is an all-in-one online office suite.
ProtonMail - Secure email with absolutely no compromises. Get your free encrypted email account today.