How to block all emails except from one IP

[Félix1]

Hello,

I use a spam protection service. It works as following :
-My DNS are configured to point to a server (sever A) which is configured to filter spams.
-If an email is not a spam, the first server send it to my mail server (server B).

But some spammers found a way to bypass the protection : They send directly their email to my mail server (server A).
So, i want to allow only emails coming from the server A IP.

How can i do this?

Thank you

 

[MorrisC]

For Mail Filter Server
On your main mail server, you need to block all incoming traffic to your incoming public smtp port such as 25 and 465 but allow access from your spam filter email server ip addresses and your ip addresses hosting websites to access those incoming public smtp port.

For Your Customers
On your main mail server, create the public incoming smtp port on your main mail server to allow your customers to use that port to send out mails.
like route port xxx to port 25 or 465...etc.

 

[Félix1]

Thank you for your answer, and sorry for my late reply... I had not the time to work on this problem.

I am not sure to understand how to do... it seems to your solution is to block outbound emails, right ? My problem is for incoming mails : I want to block spam arriving in the mailboxes of my users.

I can't configure anything on the mail filter server : its not my server.
But i can fully manage the mail server (server B), it uses plesk panel.

Can you tell me exactly what i need to do in plesk?