Private messages get marked as read by the receiver of the message?

[fury]

I sent someone a message and looked in my sent items box to read it over again so I could send them an email with the contents as well in case they were not notified of the PM... well, I went back to message tracking and it said the PM was read by that person, on the precise moment that I clicked on the message in the Sent Items box. However, this person was not online at the time. Is this a bug or what?

[Xenon]

This user has enabled to be notified via email when he gets a pm, so it automatically makes those PM's read.