MIME format option causes QuerySend to fire twice

I’ve noticed that when the local nab’s Location option ‘Format for messages addressed to internet addresses’ is set to “MIME Format” and e-mail is sent to an inet address that the querysend and other events fire twice. Does any body have an explanation as to why this happens? Also, are there conditions that would cause the events to fire a different number of times (e.g. three times).

Thanks in advance for any insight.

The Conversion Option setting (on the MIME - Conversion Options - Outbound tab in the server’s Configuration document) is “From Note to plain text”. The received message contains both text and html however.