How do I set up Exim(DirectAdmin) to accept incoming messages only from the EuropeanMX servers?

Create the file /etc/virtual/EuropeanMX_incoming_domains.
 

Add to the file the domain names that you want to secure with EuropeanMX Use one line per domain name.

Add the following part to the config file at domainlist.

domainlist EuropeanMX_domains =    lsearch;/etc/virtual/EuropeanMX_incoming_domains

Change RCPT ACL as follows:

defer
domains = +EuropeanMX_domains
!hosts = delivery.antispamcloud.com : localhost
message = Please deliver mail to the address specified in the MX records for this domain.

Save these settings and restart Exim.