Lotus Domino is an IBM server product that provides enterprise-grade e-mail, collaboration capabilities, and custom application platform. Domino began life as Lotus Notes Server, the server component of Lotus Development Corporation's client-server messaging technology. It can be used as an application server for Lotus Notes applications and/or as a web server. It also has a built-in database system in the format of NSF. From release 7, Domino server can use DB2 system as its backend database.
The Lotus Domino Email server is not well-regarded in the IMAP community because of its many violations of the IMAP specification. For example, when expunging a message, it first sends an EXISTS with a lower value than the current number of messages in the mailbox, and then it sends the EXPUNGE. This can cause clients to crash and/or remove more than one message. It also sends responses which violate IMAP syntax.