All message delivery for Mail Assure global/US/UK/EU/AU/CA/ZA comes from specific IP ranges. To prevent your firewall(s) from restricting mail traffic, make sure the IPs from this range are accepted.
These IP ranges can also be specified as: 185.201.16.0/24, 185.201.17.0/24, 185.201.18.0/24 and 185.201.19.0/24.
If you wish to use the telnet test from the webinterface or use LDAP sync/authentication, you need to authorize the webinterface IP 130.117.251.9 / 2001:978:2:6::20:10
Note - This is not required for SMTP traffic.