First Declare a temp table
DECLARE @table Table(column1 INT, Column2 INT, total int)
insert duplicate data to temp table
insert INTO @table SELECT column1, Column2,count(*) FROM Catalogue.MailingListCategoryContacts GROUP BY column1, Column2 HAVING count(*) > 1
Delete from all the data from original table
DELETE FROM Catalogue.MailingListCategoryContacts WHERE column1 IN (SELECT column1 FROM @table)
again insert into the original table
INSERT INTO Catalogue.MailingListCategoryContacts(column1, Column2) SELECT column1, Column2 FROM @table
