New version of Microsoft Exchange Server Public Folder DAV-based Administration Tool is released and can be found on http://www.microsoft.com/downloads/details.aspx?familyid=635BE792-D8AD-49E3-ADA4-E2422C0AB424&displaylang=en
Reason: [{LED=250 2.1.5 RESOLVER.GRP.Expanded; distribution list expanded};{MSG=};{FQDN=};{IP=};{LRT=}]
If you got this error checking the mail flow for a distribution group, it means the distribution group is closed and only internal senders can send e-mail to this group. When outside user sends e-mail to this group you get Reason: [{LED=250 2.1.5 RESOLVER.GRP.Expanded; distribution list expanded};{MSG=};{FQDN=};{IP=};{LRT=}] Set Delivery for this group to internal and external users and your problem will be solved.