Add a shared Mailbox.
To add a shared Mailbox you will need to follow the following steps:
1. You can now add this to your outlook mail box. Firstly you can try closing outlook and reopening it, or refreshing your internet window. If you still can't see the new inbox you can Select the File tab on the ribbon, then select Account Settings.

2. Select the Email tab. Make sure the correct account is highlighted, then choose Change followed by More Settings > Advanced > Add

3. Type the shared email address, for example Test@milestone.sandmat.uk then ok followed by ok.

4. Then choose Next > Finish > Close. You should see your new mailbox appear in your outlook window.
