Default value for 'session.auth.must-match-sender' flag doesn't allow sender to specify custom sender mailbox

[DXist]

Should we let users to choose value for session.auth.must-match-sender flag interactively in configure.sh script?

This discussion continues issue #182.

Personally the default value doesn't allow a service account designated only for email sending to specify sender mailbox address like [email protected].

From https://datatracker.ietf.org/doc/html/rfc5321#section-7.1 :

Efforts to make it more difficult for users to set envelope return
path and header "From" fields to point to valid addresses other than
their own are largely misguided: they frustrate legitimate
applications in which mail is sent by one user on behalf of another,
in which error (or normal) replies should be directed to a special
address, or in which a single message is sent to multiple recipients
on different hosts. (Systems that provide convenient ways for users
to alter these header fields on a per-message basis should attempt to
establish a primary and permanent mailbox address for the user so
that Sender header fields within the message data can be generated
sensibly.)

This specification does not further address the authentication issues
associated with SMTP other than to advocate that useful functionality
not be disabled in the hope of providing some small margin of
protection against a user who is trying to fake mail.

Letting to choose the value for this flag could be helpful because different users setup mail servers in different contexts.