# Want to Make Sure Gmail Can Not Access My Postfix Server

## dman777

I have a KVM guest that is a postfix server in which I am sending messages from my postfix server to my gmail account successfully. This is done without relaying the postfix server to gmail. 

For security reasons I want to make sure Gmail can not access my postfix server(or any outside source for that matter). I tried to reply to the email(that I send from my postfix server to my gmail account) in my gmail account to see if it would send it back to me postfix server. How come gmail didn't give me a "this message could not be delivered" message?

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## Oleg Muraviov

What is MAIL-FROM address in your outgoing mail to gmail? Is it @gmail.com?

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## dman777

no, the from would be localhost@emailserver.com.

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## Oleg Muraviov

Is there MX records defined for domain emailserver.com? Google can't access your server if not.

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## dman777

not sure...i don't think so. the domain is something i made just for my local system(my pc at my apartment). do MX records have to registered?

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## Oleg Muraviov

 *dman777 wrote:*   

> not sure...i don't think so. the domain is something i made just for my local system(my pc at my apartment). do MX records have to registered?

 

So that domain is not realy even exists in public? In this case no one can send email to you from outside your local network. And you can block 25 port by iptables on external interface to deny all connects to postfix.

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## Ant P.

You didn't receive a non-delivery message because your reply spammed emailserver.com, which is a real site.

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## dman777

no, i used a diff. domain than emailserver.com. i just posted a generic domain on the forums because i prefer not to use my real one.

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