I've had a few questions this week asking how to read mail on a smartphone and not mark it read in Outlook. The reason the users want to do this is so they don't forget to respond when they are back at the computer and nothing jogs the memory like an unread message, but they don't want to give up the ability to quickly check their email on the phone.
Unfortunately, this is not possible when you use ActiveSync (or BES) to check Exchange server email, as all changes are synced back to the Exchange Server and to Outlook. Using POP3 on the phone might be an option, but it's not a good option as changes won't sync back to the server and it won't include calendar and contacts.
My suggestion: a search folder configured to display new mail from the last day or so. You can review everything that arrived 'today' in the search folder and mark mail unread as needed. A custom view could be used instead of a search folder. The filter will be the same for both: On the Advanced tab of the filter dialog, enter Received on or after Yesterday. Received on Today, or Received on or after 2 days ago will also work.
My unread mail is marked as read but I didn't read it
When users complain about mail in their Exchange mailbox being marked as read without the user actually reading it, it usually means they're using a handheld device to check their email account. When the device uses POP3 to check for new mail, all new messages downloaded will be marked as read on the server.
Blackberry users (not using BES) can avoid having their mail marked as read by connecting through OWA. If the account is set to wireless reconcile on the device, messages will be marked read on the server when they are read on the device. If reconciliation is disabled in Email Options on the Blackberry, messages read on the Blackberry will not be marked as read in Outlook.
For instructions, see "Associate a Microsoft Outlook Web Access email account with a BlackBerry Internet Service account".
Note: while it is possible for mail to be marked as read in the preview pane just by selecting a message, only the currently selected message would be affected, not all messages. This setting can be changed in Tools, Options, Other tab, Preview Pane (or Reading Pane). In Outlook 2010 and 2013, Reading pane options are on the Folder tab, Reading pane button. Disable the setting for Mark after viewing for xx seconds.