Horde Vacation - bug or WAD??

When a user enables a vacation message in Horde, everything works until the same sender submits more than three messages to the vacationer. The 4th and subsequent messages generate the following message in the qmail log: (reformated by qmail-track.pl)

2006-07-06 09:27:42.542401500 delivery 398356: success: AUTORESPOND:_too_many_received_from_[xxx@yyy.zzz]/did_0+0+1/

Now, I am greatful that responder loops are avoided. However, in my case at least, the email message being received is never delivered to the vacationer’s in box.

This seems undesireable. Is it a bug?