Hi,

I have installed postfix for SMTP reasons. I also want to use postfix for internal email traffic and fetch the mail from our ISP and distribute it to the internal network to Mail User Agents (Thunderbird clients).

While installing postfix, it asks for "network block"
As far as I can understand, it means from which ip ranges postfix accepts mail requests. My LAN network is 128.10.1.0 so I should have an ip range of: 128.10.1.0/28?

If I am correct, the /28 means 128.10.1.1 till 128.10.1.255?

I would really appreciate some info about this. I want to know if I am correct and if not, what should I do to allow smtp for the LAN?

Yeah that's about right, but /24 is .0 to .255, /28 covers .0 to .15 only (and blocks of 16 IP's thereafter)

So the network block is blocking IP-adresses? Mmm, so if I leave it open, the postfix will be an open relay for all spammers to be used? What if I want to allow some local PC's to send mail, but block the rest of the world?

And how do I do this?

Well then you define what your local subnets are, hence them asking you that question. In a simple way you just say that you can send mail to the service if 1) you are in subnet x, y or z, OR 2) you are sending mail to example.com or such.

I need to think this over Since I am reading and reading everywhere