Mail

Microsoft Exchange – On Premis or Hosted 365

Microsoft Exchange provides full and Seemless connectivity Between Desktop – Webmail and Mobile Devices. Group emails and Calenders.

Compare
https://www.microsoft.com/en-au/microsoft-365/business/compare-all-microsoft-365-business-products?&activetab=tab:primaryr2

Lotus Notes and domino – cost effective Mail and group applications

IBM® Domino® Express is a security-rich, full-featured application environment for email, business and collaborative applications. This set of IBM messaging and collaboration offerings enables companies to acquire, deploy and use the capabilities of IBM Domino software. IBM Domino Express offerings are packaged and priced to provide cost-effective functionality for midsize companies with less than 1,000 authorized users.

IBM Domino Express is:

• Cost-effective—bringing enterprise features to midsize businesses at an affordable price. Per-user pricing is available.
• Security-rich—helping to protect your data with encryption and engineered to resist viruses.
• Easier to manage—automated installations, policies and monitoring minimizes your administration needs.
• Mobile—helping you stay connected using a variety of mobile devices while helping protect business assets.
• Compatible—supports thousands of independent software vendor applications.

Alt-N MDaemon – MDaemon from – For a Smaller site just wanting their own mail server.

 MDaemon Messaging Server