One feature that may be helpful, especially to users
whose mail servers reject any unauthenticated
connection, would be the support of SMTP-AUTH usernames
and passwords. Of course, consideration would have to
be given concerning the security implications of
including these credentials as either (1) variables set
directly within the script itself or (2) options set in
the Soupermail configuration files. However, these
security implications should mostly parallel those that
come with including SQL credentials in either of these
locations (of which configuration files is the
currently supported choice). The security implications
would include (off the top of my head) making sure your
script is not code-readable from the public side if the
credentials are stored as variables in the script,
and/or making sure your configuration files are not
publically readable via server configured file excludes
or the new Private Root function. There may be more to
consider, but I'm just throwing the idea out there for
right now.