I missed the one field.
This should do it.
Dim strSQL As String
strSQL = "INSERT INTO MCEMAIL (CUSTNO, FULLNAME, EMAIL, REGID, CLASSINFO) " & _
"(SELECT DISTINCT CUSTNO, FULLNAME, EMAIL, REGID, NULL AS CLASSINFO " & _
"FROM MCTEST2 " & _
"WHERE CUSTNO=" & rstInsert![CUSTNO] & " AND...