PMDF actually supports two separate and distinct delivery receipt request mechanisms: envelope level delivery receipt requests as defined by RFC's 1891--1894 (often referred to as NOTARY), and the ad-hoc header style delivery receipt requests that were all that existed prior to NOTARY. (PMDF layered products such as PMDF-LAN, PMDF-MR, PMDF-MB400, PMDF-X400, and PMDF-XGS also support "foreign" delivery receipt mechanisms, if they exist, to the extent possible.)
Newer mailers can support the NOTARY delivery receipt mechanism; support for the NOTARY mechanism can be expected to grow. Older mailers, however, such as older sendmail implementations, can not yet support NOTARY and the only hope of getting back delivery receipts from such mailers can be to send the delivery receipt requests in the old header style.
The channel keywords
reportsuppress when used on the L channel control whether
the delivery receipt requests resulting from a
(delivery-receipt) comment (or use of PMDF MAIL's
/DELIVERY_RECEIPT qualifier) are header style requests, NOTARY style
requests, or both, or whether no receipt requests are generated at all.
reportheader is the default. To maximize the chances of
receiving back requested delivery reports, whether the remote receiving
side supports the header style request mechanism or NOTARY, one can set
reportboth; however, note that if a message with both
style requests is delivered via a mailer (such as PMDF) that supports
both styles, then two delivery reports can be generated, one
for each form of request.