#2 pop before smtp or smtp password

[Anonymous]

Hi, I am triing to use this smart and simple mail
server for my personal email.

Because the server will be in internet 24x7 I like to
add some more security think.

I have tried relaying denied filter. But I like to add
a features like pop before smtp or a smtp password. Any
suggest to make this?

You can email me to:

d@vide.bz

Thanks!