DELIVER screens and automatically processes your incoming mail based on guidelines that you provide. Different actions can be taken based on a message's envelope or header addresses, subject, or content. These actions include delivering the message, filing the message away, forwarding the message, or even invoking a DCL command procedure to perform complex processing. Any actions taken occur immediately upon receipt of each message; you do not need to be logged in at the time a message is received in order for actions to be taken on your behalf.

DELIVER is modelled after the MAILDELIVERY facility of the MMDF mail system. DELIVER is, however, completely distinct from MMDF and the formats of .MAILDELIVERY files for MMDF and MAIL.DELIVERY files for DELIVER are dissimilar.