alter table SendMailList
add key_col int not null identity(1,1)
go
delete from SendMailList
where exists
(
select * from SendMailList as t2
where t2.EMail=SendMailList.EMail
and t2.key_col>SendMailList.key_col
)
go
alter table SendMailList
drop column key_col
delete from SendMailList
where exists
(
select * from SendMailList as t2
where t2.EMail=SendMailList.EMail
and t2.id>SendMailList.id
)