Building on the US Mail Formatted Invitation idea I just submitted...

Consider partnering with one or more "Mail Service Providers" (National or Regional as needed).

1. Once you get the Invitation format set-up for the Window Envelope
2. Allow the User to select All or Individual Bidders to send to via US Mail as they need
3. The User submits the Mail List
4. The Mail List goes to the National or Regional Mail Service Provider, who prints, stuffs, and mails the ITBs out within 24-48 hours.

Assumption:
1. Mail Service Provider charges your office $0.35 each (Guess as they are a Mass Mailer will have some kind of deal with the USPS)
2. You charge us the $0.35 + $0.15 = $0.50 per Individual Mail Piece
3. We don't have to suffer through days of printing, stuffing, reopening, restuffing, how does mail merge work with this version? !@#$, and finally getting to the Post Office... where we have to purchase individual stamps and put them on the letters one-by-one-by-one... because this branch doesn't have a Postage Meter!? WTF!?

Us: So much headache saved!
You: Easy Money...