Sieve redirect and Cyrus Aggregation ( murder )

[Lucas Zinato Carraro]

   I have some doubts about sieve.
In a enviromment with cyrus aggregation ( murder )
when i use:

redirect "my-address at somewhere.else.com";


its necessary a MTA running in backend (or frontend ) ?
How redirect works ?

I can specify a remote SMTP server for
 redirect  and vacation message ?

Regards
Zinato