ERROR: Error while reading data from host mail.example.:25

is your SMTPd listening on your public IP?

I think yes because this is the telnet result to my public ip:

$ telnet 10.300.432.403 25

Trying 10.300.432.403…

Connected to 10.300.432.403.

Escape character is '^]'.

220 mail.example.com ESMTP Postfix

You might have better luck posting real information; for now, without trying it from here, all I can come up with is "huh, that's weird."

@shams:

I think yes because this is the telnet result to my public ip:
From outside your Linode? It'll still use lo if you do it from your Linode.

@jed:

@shams:

I think yes because this is the telnet result to my public ip:
From outside your Linode? It'll still use lo if you do it from your Linode.

The traffic may flow over "lo" but the IP addresses used would be the public ones and so would be a sufficient test to determine that the daemon is bound to the public address.

It's not enough to test firewall rules.

@sweh:

It's not enough to test firewall rules.
What I was getting at.

thanks for the replies, but i didn't get any idea what to do, i just test my mail server and i can send emails from my mail server to the net but can't get the emails from the net? can it be also my isp problem that blocks the port 25?

@hoopycat:

You might have better luck posting real information.