Admin By Request uses port 443 and the IP addresses and API URLs that need access through firewalls are as follows.
If your data is located in Europe (Netherlands):
IP: 104.45.17.196
DNS: api1.adminbyrequest.com
DNS: macapi1.adminbyrequest.com
DNS: linuxapi1.adminbyrequest.com
If your data is located in the USA (East):
IP: 137.117.73.20
DNS: api2.adminbyrequest.com
DNS: macapi2.adminbyrequest.com
DNS: linuxapi2.adminbyrequest.com
If your data is located in the UK:
IP: 85.210.211.164
DNS: api3.adminbyrequest.com
DNS: macapi3.adminbyrequest.com
DNS: linuxapi3.adminbyrequest.com
If your data is located in Europe (Germany):
IP: 9.141.94.162
DNS: api4.adminbyrequest.com
DNS: macapi4.adminbyrequest.com
DNS: linuxapi4.adminbyrequest.com
If your data is located in the USA (West):
IP: 172.184.188.29
DNS: api5.adminbyrequest.com
DNS: macapi5.adminbyrequest.com
DNS: linuxapi5.adminbyrequest.com
If your data is located in Asia (Singapore):
IP: 52.230.54.129
DNS: api6.adminbyrequest.com
DNS: macapi6.adminbyrequest.com
DNS: linuxapi6.adminbyrequest.com
Wherever you are, you can also use api.adminbyrequest.com, but the regional URLs will likely be more responsive.