Notification of subfolders inside inbox in outlook 2016

Solution 1:

In the last version of Outlook (2016/365), it's hidden under the 'Rules' button in the ribbon:

Select 'edit rules', and select the protocol your e-mail account uses under 'Client rules'. There you can just click the + icon and add a rule for every subdirectory as follows:

• Rule name: Anything
• When a new message arrives: all messages
• Execute the following action: Play Sound (or Show Notification)

Click 'OK' and repeat this for every subdirectory you want to receive a notification for.

Solution 2:

Outlook new mail notification only works for emails in Inbox folder. If you want Outlook to show alerts for emails moved to subfolders, add the following action in the inbox rule you used to move the emails.

Solution 3:

For those like me who were struggling to find the "display a Desktop Alert" setting, it's on the next page of the dialog.

In the Rules wizard, click the Next button so that it says "Step 1: What do you want to do with the message?"