• Maildir — deliver all messages to a local qmail-style maildir
• Mboxrd — deliver all messages to a local mboxrd-format mbox file with fcntl-type locking.
• MDA_external — use an external message delivery agent (MDA) to deliver messages. Typical MDAs include maildrop, procmail, and others.
• MultiDestination — unconditionally deliver messages to multiple destinations (maildirs, mbox files, external MDAs, or other destinations).
• MultiSorter — sort messages according to the envelope recipient (requires a domain mailbox retriever) and deliver to a variety of maildirs, mbox files, external MDAs, or other destinations based on regular expressions matching the recipient address of each message. Messages not matching any of the regular expressions are delivered to a default "postmaster" destination.
• MultiGuesser — sort messages according to addresses found in the message's header fields and deliver to a variety of maildirs, mbox files, external MDAs, or other destinations based on regular expressions matching those addresses. Messages not matching any of the regular expressions are delivered to a default "postmaster" destination.
• MDA_qmaillocal — use qmail-local to deliver messages according to instructions in a .qmail file.