Automatically marking messages as read

To mark an individual message as read or unread, select the message, click the Edit menu, and then click Mark as Read or Mark as Unread.
To mark all newsgroup messages as read when you quit Outlook Express or go to another newsgroup, click Options on the Tools menu, and on the Read tab, select the following check box: Mark all messages as read when exiting a newsgroup.
To mark all messages in a selected newsgroup as read, including messages not yet downloaded, select the newsgroup in the Folders list, and click Catch Up on the Edit menu.
This is handy, for example, when you return from vacation and don't want to download all unread messages, but want to start reading the current ones.

To mark all the messages in a given newsgroup conversation* as read, select either the original message or any of its replies, click the Edit menu, and then click Mark Conversation as Read.
*A conversation is an original message and all its posted replies. Conversations are sorted and grouped according to the title of the original message. For example, a conversation that starts with a message titled "Tips for Labrador owners" includes all of the replies titled "RE: Tips for Labrador owners."

Mail and news messages are automatically marked as read after they are open for a certain length of time. If you don't want messages automatically marked, you can click Options on the Tools menu, and on the Read tab, clear the following check box: Mark message read after displaying for x seconds(s).