Linux Mail Server Setup and Howto Guide

Hi admin,

I have 2 question about postfix and my Postfix using dovecot:

1. In postfix, what file I must to change so that I can limit attachment size up to 10 MB?

2. When I try to telnet smtp for other my networks, i see the result like this:

# telnet example.com 25
Trying 123.45.67.89…
Connected to localhost.localdomain (123.45.67.89).
Escape character is '^]'.
220 mail.example.com ESMTP Postfix
ehlo example.com
250-mail.example.com
250-PIPELINING
250-SIZE 10240000
250-VRFY
250-ETRN
250-AUTH PLAIN LOGIN
250-AUTH=PLAIN LOGIN
250-ENHANCEDSTATUSCODES
250-8BITMIME
250 DSN

I think it is dangerous for my mail server so everyone can send spam or anything else for my mail server from telnet. I want to my mail server like this:

# telnet example.net 25

Trying 123.45.67.98 …
Connected to example.net (123.45.67.98).
Escape character is '^]'.

220 example.net ESMTP,  No Unsolicited Commercial Email (U.C.E) Allowed. This SMTP is not for spammers iklan!!
421 4.4.2 example.net Error: timeout exceeded

So, what should i do in postfix? And what the term of that phenomenon like that?

Thank You for you answer.

Thank You admin for your quick response.

But my question is not how to changing the banner message. My question is how we configure postfix so when someone try to telnet to my mail server by command:

# telnet example.com 25

it shows the notice like this:

421 4.4.2 example.net Error: timeout exceeded

and not like this:

# telnet example.com 25

Trying 123.45.67.89…

Connected to localhost.localdomain (123.45.67.89).

Escape character is '^]'.

220 mail.example.com ESMTP Postfix

Thank you for your answer.