The present invention is directed to automating the sending of campaign messages in computing environments. Campaign scores are determined for messaging campaigns and eligible recipients are assigned to campaigns with a higher score. More specifically, eligible recipients are assigned to a particular messaging campaign if the campaign is the "best" campaign for each eligible recipient based on the campaign score. Additionally, a portion of the eligible recipients are reserved as a control group for each campaign. After campaign messages have been sent out to assigned recipients, the behavior of the recipients who received campaign messages and the behavior of the control group members are differentiated to update the campaign's score. Continually updating campaign scores makes it possible to continually update which campaign is best for a particular recipient.