How do I set up PostFix to accept incoming messages only from the EuropeanMX servers?

To limit the delivery of incoming messages in PostFix to EuropeanMX servers, please follow the steps below.

Variant 1: Limit delivery of messages for all domains of the server to EuropeanMX

1

Create a file /etc/postfix/access and add the following content:

185.201.16.200 OK
185.201.17.200 OK
185.201.18.200 OK
185.201.19.200 OK
antispamcloud.com OK

2

Execute the following command:

postmap /etc/postfix/access

3

Add the following content to the /etc/postfix/main.cf file

smtpd_client_restrictions = check_client_access hash:/etc/postfix/access, permit_mynetworks, reject

Or if you have already defined smtpd_client_restrictions, add the following at the beginning of your definition and replace permit with reject at the end:

"check_client_access hash:/etc/postfix/access"

4

Restart PostFix.

/etc/init.d/postfix restart

Variant 2: Limit delivery of messages for certain domains to EuropeanMX

1

Add the following content to the /etc/postfix/main.cf file:

smtpd_restriction_classes = EuropeanMX
EuropeanMX = check_client_access hash:/etc/postfix/EuropeanMX, reject
smtpd_recipient_restrictions = check_recipient_access hash:/etc/postfix/protected_destinations, permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination

2

Create the file /etc/postfix/EuropeanMX with the following content:

antispamcloud.com OK

If you also send and receive internal messages, then you must also add the localhost and localdomain to the file in the following format

domain.example OK
localhost OK
localdomain OK

3

Create the file /etc/postfix/protected_destinations and add the domain(s) you want to restrict in the following format:

example.com EuropeanMX
example.net EuropeanMX

4

Postmap both files.

postmap /etc/postfix/EuropeanMX
postmap /etc/postfix/protected_destinations

5

Restart PostFix in order to apply the changes.