SMTP port 25 blocking issues????

Hi Ya’ll, we’re an ISP and we provide our customers with our own email dns addresses. We block port 25 for obvious reasons, but my problem is that a customer cannot use any other DNS email because of the port 25 blocking. I’ve tried making an accept rule in ip-firewall-filter rules that allows port 25 traffic to a specific smtp ip address to go through, but it isn’t working. Any tips?
Mac

I use a simple rule, in this example my main (ISP) Mail server is 1.1.1.1 and a customer has a mail server someone else hosts at 2.2.2.2/32 and another customer at 3.3.3.3/32.

This rule blocks an destination TCP port 25 that is not destined for the IP addresses listed in the address List SMTP-addr.

/ ip firewall filter
add chain=forward protocol=tcp dst-port=25 dst-address-list=!SMTP-addr action=drop comment=“” disabled=no

/ ip firewall address-list
add list=SMTP-addr address=1.1.1.1/32 comment=“ISP SMTP” disabled=no
add list=SMTP-addr address=2.2.2.2/32 comment=“Cust1 SMTP” disabled=no
add list=SMTP-addr address=3.3.3.3/32 comment=“Cust2 SMTP” disabled=no

I hope this helps.

Done, but it doesnt show any packets.