Duplicate Mail when user in group mail

Hello

Exchange server 2013 CU1 on win2012

• Have  Universal Distribute Group mail name is Group1 . UserA is in member of Group1

When userA Send email on outlook and web-mail to Group1. UserA receipt duplicate mail at sometime every send to Group1

(UserA don't have any mail rule)

• I try to  new created Universal Distribute Group name is Group2 . UserA is in member of Group2

When userA Send email on outlook and web-mail to Group1. UserA receipt duplicate mail at sometime every send to Group2

• If User A don't member of Universal Distribute Group name is Group3 .

When userA send to Group3 , Usera don't receipt duplicate mail .