Package msmtp to be a /usr/lib/sendmail replacement

[tabbott]

Getting msmtp working as a sendmail replacement will improve linerva security (by removing dependence on sendmail) and make many more mail senders on Debathena machines able to send authentic email. This probably involves:

• Modifying the /usr/lib/debathena-mstmp script to remove the -t argument and perhaps fail to using outgoing-legacy when tickets are not available.
• Make a new debathena-msmtp-sendmail package (from the

debathena-msmtp-config source package) that Provides: mail-transport-agent and includes the new script as /usr/lib/sendmail

• testing it a whole lot with clients like pine, evolution, mail, mutt, etc.