Message Recall works differently for different users

I am having a problem with Outlook Recall message (in internal Exchange
Server).
For some users the messages waits for user to open the Recall message before
deleting the original. But for some others both original and the recall
notification reach the mail box but in few secs both messages gets deleted
(i.e. user will never know that something reached his mail box). Can someone
know if there are any settings causing this difference? or is it a random
thing?

PS: Assume that the original message is unread.

Version of Outlook is 2003.