Set public folder to accept NDR

1.      Locate user A’s distinguishedName

Get-User “User A” | Fl DistinguishedName

2.      Launch ADSI Editor, go to “CN=Microsoft Exchange System Objects”, right-click the PF1 object, and then go to “Properties”

Notes: PF1 must be mail-enabled

3.      In the “Attribute Editor” tab, locate “publicDelegates” attribute, and then copy user A’s DistinguishedName into it

from 

https://social.technet.microsoft.com/Forums/office/en-US/d341ff3f-9a8c-40c7-ab04-0a1655047041/public-folder-not-accepting-ndr?forum=exchangesvrgenerallegacy