Advice on E-mail Filter

[Cecoban S.A. de C.V. Oswaldo Espinosa Cuervo]

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Hi all.

I know maybe this is not a good question but i have some doubths about Email 
Filter.

I see some of you have a SMTP relay or a e-mail filter deployed on your 
organizations, which product do you think is the convenient to buy???

Thanks in advanced.

Sorry, but i'm a bit new on the stuff.