[Mass Email Sender] SMTP authentication and legal footer

Hello everyone,

We are looking for ideas to have better communication with our sites' owners by sending news (changelog, tips, new features, etc). We think that the "Mass Email Sender" could allow us to do that easily.

1. On a site, we use WP Mail SMTP to authenticate outgoing emails, how can we do that with Mass Email Sender since it's a network administrator feature and there doesn't seem to be any setting for that?

2. Can the HTML template be customized? Among other things, we'd like to add our physical address in the footer so our emails are legal according to the Canadian spam law (CASL) which applies to the US as well.

Kind regards,