Failed to Recall Message in Tracking Email

[DianeM]

I am sending a message out to 5 people. In my new message
I go to the Options button and select "request for
delivery receipt for this message and a read receipt for
this message. When I go to the sent items folder and view
the tracking tab to see the status, it shows that the
message was delivered to all 5 people, however, under the
information section on the Tracking tab it shows the
following

This message was send on 1/18/2005 9:42 A>M>
Status Totals: delivered to 3 recipients; failed to
recall from 1 recipient; not read by 1 recipient.

I did not try to recall the message, but I don't
understand why the status shows failed to recall from 1
recipient.

Can anyone help explain what this means.