Messages in IMAP folders is not listed in Outlook 2013
The issue is caused by the following Microsoft updates:
It can be resolved in two ways:
Disable the "Show only subscribed folders" option in Outlook
1.1. Go to FOLDER > IMAP Folders
1.2. Uncheck "When displaying hierarchy in Outlook, show only the subscribed folders.".
1.3. Force Send/Receive within Outlook.
By changing the "Root folder path"
2.1. Go to File > Account Settings > Account settings >
<Problem IMAP account>> Change... > More Options... > Advanced.
2.2. Set Root folder path to Inbox and force a Send/Receive