Lotus Notes is commonly deployed as an end-user email client in larger organizations, with IBM claiming a cumulative 145 million[citation needed] licenses sold to date. (IBM does not release the number of licenses on current maintenance, nor does it track number of licenses in current use.)[citation needed]
When an organization employs a Lotus Domino server, it usually also deploys the supplied Lotus Notes client for accessing the IBM supplied Lotus Notes application for email and calendaring but also to use document management and workflow applications. As Lotus Notes is a runtime environment, and the email and calendaring functions in Lotus Notes are simply an application provided by IBM the administrators are free to develop alternate email and calendaring applications. It is also possible to alter, amend or extend the IBM supplied email and calendaring application.
The Domino server also supports POP3 and IMAP mail clients, and through an extension product (Domino Access for Microsoft Outlook) supports native access for Microsoft Outlook clients (now with limited support).[7]
Lotus also provides iNotes (in Notes 6.5 renamed to "Domino Web Access" but in version 8.0 reverted back to iNotes), to allow the use of email and calendaring features through Internet Explorer and Firefox web browsers on Windows, Mac and Linux. There are several spam filtering programs available, and a rules engine allowing user-defined mail processing to be performed by the server.