Or because you didn't mark it read in preview. They requested a read receipt
and you didn't mark the message read.
Depending on your version of Outlook, you can change the setting to never
send a receipt or ask for approval each time (tools, options, email options,
tracking) - I like to be asked, just so I know who requests receipts. If
your outlook supports allowing a choice, tell them that read receipts are a
poor way to determine if a message was read. To prove it, make a copy of the
mail and delete it unread then reply to the copy (but don't send a receipt
for the second one). They'll get an unread plus your reply. <g>
If you want to be naughty while making a point, make a lot of copies and
delete all unread.
--
Diane Poremsky [MVP - Outlook]
Author, Teach Yourself Outlook 2003 in 24 Hours
Coauthor, OneNote 2003 for Windows (Visual QuickStart Guide)
Need Help with Common Tasks?
http://www.outlook-tips.net/beginner/