JMAP has an extension for this -- RFC 9007's MDN/send -- and Stalwart does
not implement it, so ihasmail assembles the RFC 8098 multipart/report itself
and sends it the long way round: raw MIME uploaded as a blob, imported,
submitted. That is also why the receipt lands in Sent, which is where it
honestly belongs.
The plumbing is the easy half. A receipt tells whoever asked that the address
is live and when the message was read, to an address the sender chose, so the
refusals are the feature: nothing marked Auto-Submitted (RFC 3834, or two
servers answer each other forever), nothing carrying Precedence bulk/list/junk
or a List-Id, nothing already acknowledged, nothing that never arrived. A
receipt aimed anywhere other than the sender is offered, but says so first.
There is no "always send" setting, only ask or never.
Sending is recorded with RFC 3503's $mdnsent keyword on the original rather
than remembered locally, so a second look -- or another client entirely --
knows not to ask again. Non-ASCII parts go base64 rather than 8bit, so
nothing rests on 8BITMIME surviving every hop.
Verified against the mock end to end: the blob uploads, the receipt imports
and submits, and the original reads back marked. Not yet exercised against
the live server.
jcoffey-dev
b0944b2f42