User story: I was not sure whether I had sent a welcome email to jmk on stewards, and there is no way to verify this (other than looking at the log file).

Each sending of a welcome email should be stored in the database, as a posting (or as a notification message? What are the differences between postings and notify? postings get "approved"; each posting becomes one email message; postings have a date but not a time (at least right now... we should probably add a "sent" timestamp).

Also on the Stewards site the admin will probably want to see when a user has received an invitation, when they defined or changed their password or email address, ...