A user recently switched from POP to Exchange Server. When accessing his email in Outlook via POP, a folder would autoexpand whenever a subfolder received new message. However this does not happen with his Exchange account.
"How can I get the subfolders to autoexpand when a new message arrives in one of these subfolders?"
Sorry, you can't force it. The folders either expand when messages are moved into them or they don't. There isn't an option you can change to make it work.
When Outlook moves your messages to folders as it downloads them, it may expand the folder tree so that folders with new messages are visible. Not all versions and builds support expanding folders but when they do, it should always work. In older versions, some updates broke it and others fixed it, so if it doesn't work, check for updates.
POP3: If it's not working, there is nothing to enable or change to make it work.
Exchange: Unlike POP3, messages are not moved to folders by rules only when Outlook downloads your mail to the local computer. If the rule does not have "(client-side)" after the name, the rule runs on the server as the mail is dropped into the mailbox, before its downloaded by Outlook. The folder will never expand when the message is moved by server-side rules.
If a rule is marked (client-side) you can't force it server-side (except by editing the rule to remove the client-side conditions), but server rules can be forced to the client-side by adding flags, categories, or other conditions that are applied by the client only.
For more information about client-side and server-side rules, see Server-side vs. client-side rules
Published August 26, 2011. Last updated on October 31, 2011.