Outlook 98 – error when sending message on behalf

hi

I have a client using an ancient Windows 98/Office 98 PC. She has full delegate Editor level permissions to her managers mailbox and can see Inbox, Calendar, Sent Items etc. However when she tries to send or reply to a message from his Inbox she gets the error “Cannot save sent messages to a folder marked read-only. The message will be saved to the Sent items folder. Do you want to continue?”

The message does send when you hit continue but the message is annoying. The question was posted here a few years ago and someone recommended a Microsoft KB article but it does not seem to be there any more. Any ideas gratefully accepted.

Thanks
D