3. On the Exchange Admin Center recipients tab, click groups from the top menu, click the + button and choose Distribution group.
5. Double-click on the created group.
6. Click on delivery management from menu on left. Then select Senders inside and outside of my organization. This will allow users from outside your domain to email this address.
9. In Outlook (2007, 2010, 2013 or 2016), open a new message and perform the following:
a. Click on the Options tab.
b. In the Show Fields section, ensure From is selected.
c. On the new message, click the From drop down menu and select Other E-mail Address....
d. In the Send from Other E-Mail Address popup window, click the From drop down menu and select the Global Address List.
e. Find the group you created previously and double-click the group.
f. Click Ok when finished. You will see the alias address listed in the From field.