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.