For a business with a few users, or a few thousand users, POP is not enough. Businesses often choose a proprietary email system such as MS Mail, MS Exchange, Netscape server, QuickMail or Communigate. Upgrades often require a transition period, retraining and a lot of down time. Provides the features required for collaboration, such as server storage. Off line copies of messages can be stored and synchronised with the server.
Users can move from one workstation to another and still see all their email and mailbox structure.
Several people in a work group can each access a shared account, and others can see immediate action. Drafts of outgoing messages can be stored on the server. Access privileges can be set for each user of a shared mailbox. Each message can have various flags set. Although IMAP is a long established standard, software support, especially for the Mac OS, has only escalated fairly recently.