Third-party blogs have had these steps in the past but now there are official MS posts for how to do this. It’s sometimes needed when customers accidentally delete them, which can result in mail flow and other issues.
2016 Article
https://technet.microsoft.com/en-us/library/mt829277%28v=exchg.160%29.aspx
2013 Article
https://technet.microsoft.com/en-us/library/mt829264(v=exchg.150).aspx
Advertisements