I envision being able to select all or some of the message senders and date selectors so you could show messages sent in between multiple dates. This report would be useful if you had ISP 1, ISP 2 and paid for a third-party relay service that you wanted to use mainly for bulk mailings. The report would show how many messages were sent and the cumulative size sent out through each out mail sender in between the dates that were selected. With total number of messages sent for all of the message senders at the bottom of the report. This report would allow you to answer the following questions.

1 do I need to pay for the next tier in my third-party relay service?
2 can I drop to a lower tier of messages sent per month?
3 maybe create domain filters limiting what can and what cannot go out through each out mail method. For example limit the third-party relay service to the bulk mailing while allowing everything else to go out between the two ISPs.

In summary this report would show message count and total message size for each message sender to the Internet.