Installing Postfix instead Exim4

[Camaleón <noelamac@gmail.com>]

Hello,

I am in the process of installing some servers with Lenny and would like to
install Postfix instead Exim, as I'm more used to it.

I cannot see any option (under expert installer) to choose Postfix instead
Exim so not sure about the correct procedure to achieve this.

1/ Should I install the default "mail server" template and once the system
is fully installed then go and install Postfix?

2/ Or is there any available parameter I can pass the installer to select a
specific mail server for installation, instead using the default one?

Thanks!

Greetings,

-- 
Camaleón