What's the maximum number of members you can add to a Distribution group? The member attribute of groups - both Distribution and Security groups, is a multi-valued attribute. So the answer is more about how many values can a multi-valued Active Directory attribute hold. Many of you may remember the recommendation of 5000 values in a multi-valued attribute in Windows 2000, and the fact that the limitation no longer exists in subsequent versions. So what's the actual limit? Or is there a limit at all?
Source:→ Exchange Team Blog