SymptomsWhen the user logs into their Webmail, left sidebar shows more unseen/unread messages than are actually in the Inbox.The title bar is correct in it's numbers, but not the side bar. Even marking all as seen or read doesn't lower the number or unread messages.
ResolutionMost likely you have deleted some messages without reading them. Since deleting the message does not actually remove the message from the Inbox it is still counted as an unread message by the mail program. You can view the unread deleted items by clicking the "Show Deleted" link on the right at the bottom of the list of mails in Inbox. Unread messages will be in bold type. Deleted messages have a line through them. If you click the Purge Deleted link (which will permanently remove the deleted items) next to the Show Deleted link the message number indicator will update to show the number of unread messages that have not been deleted.
You can change Horde behavior , so it moves the deleted messages out of the Inbox to a Trash folder. This will simulate how regular mail programs, like Outlook Express, handle deleted messages, and it will keep the message count indicator showing just the messages that are not read and haven't been deleted in the Inbox. To enable the trash folder click Options -> Mail -> Deleting and Moving Messages. Check the box next to "When deleting messages, move them to your Trash folder instead of marking them as deleted?" Then select the Trash option in the Trash Folder drop down box. Click Save Options to save the settings. Remember to Empty the trash periodically.