saber cuantos correos tengo de outlook

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Piensale poquito no?

Código MySQL:

select count(*), completo from(
select substring(correo,1,INSTR(correo,'.')+1) as completo from(
select substring(email, INSTR(email,'@')+1, len(email)) as correo from tabla
) as t1 
) as t2 group by completo