Chapter Members are added to the Member List and Only Enabled Members List by programming that occurs in ProDEP. ProDEP is a process which pulls member data from PMI once a day, adding new members and expiring lapsed members. See Extensions, ProDEP and Community Builder documentation.
This is the original Members list which is auto-populated during ProDEP import daily. It contains both current and FORMER members, so DO NOT USE to send to current members. Use the Only Enabled Members List.