By default, when you click on a new email notification from the Notification Center, that email is opened using the Mail app. However, if you have Outlook 2016 locally installed, you may want to use it instead.

Notification Center: received e-mails

Changing that behavior is a matter of setting the predefined association in Setting -> Predefined App and you can easily reach that setting page searching to predefined app and selecting the option related to the e-mail case.

Search for “Predefined App” and choose the e-mail case

Settings -> Predefined Apps

Settings -> Predefined Apps – Select Outlook 2016

May be, the new setting should have effect only after some time (as it happened to me) or possibly after a reboot.

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Note that there is also another settings option page related to what app is associated to every file extension type,: here you can find by default set to Outlook 2016 the following file extensions: .vcs .vcf .pst .oft .ics .hol .eml … and no one to Mail app.
But this settings is not related to the subject of this post, …  even though it can confuse!

P.S. This method doesn’t work to me (anymore?) … I am a bit confused, so I asked help to the Microsoft Community forum : let’s wait for some replies

Someone suggested me to check the property “Make Outlook the default program for E-mail, Contacts, and Calendar” from the Outlook settings (following the steps on this link) … but it was already checked!

Some other good guy suggested the following workaround to turning the notifications on for the Outlook app, following the steps below:

1. Go to Settings.
2. Click System then Notifications & actions.
3. Click on Outlook 2016.
4. Check if Notifications is On and set the Show in action center switch On.

The issue still persisted, so I tried also to turn Mail app notifications off instead:

1. Open Mail app then click Settings (gear icon on the bottom).
2. Select Notifications.
3. Turn off Show notifications in the Action Center to stop showing new emails in the Action Center.

However things continue not to work properly. As you can see from the following screenshots, now I succeeded to have ONE Outlook 2016 notification in the Notification Centre side bar (only the first one … then, for the following received emails, I did not receive anymore notifications in the Notification Center but only the temporary popup right bottom window): anyway that single email notification was greyed and clicking on it did not opened the related email with Outlook 2016, but simply disappeared from the Notification Bar, to appear again after a while, closing and re-opening the Notification Center side bar, always grayed and with the same strange behavior.

Waiting for some more suggestions … 😦

I even did the quick repair of Office 2016 but nothing changed in the behavior: as I said, each email notification is shown in the Notification center side bar but it is greyed and clicking on it only close that notification and does not open the email with Outlook 2016 …

Therefore I believe that there should be a missing integration of Outlook 2016 with the notification center. It is the only application I see having a notification grayed!