smmapd is a framework for workers on the sendmail (>8.13) socket map. It directly contains a sender address verifier and a Cyrus IMAP mailbox verifier (dedicated to Cyrus IMAP <2.2, but also works we later version).
Cyrus IMAPd is a popular IMAP server that surfaces a rich interface for extending its functionality. The Cyrus IMAPd Utilities project brings together maintenance utilities, graphical front-ends, and API handlers (such as notification daemons).