How can we improve WHMCS?

The actual Domain Resolver only checks for the A record of the main domain name of the account. I believe it should also try to resolv the MX server of the domain to see if it is pointing to one of the servers IP because some clients are only hosting email services on the servers.

So for example, if our server IP is 2.2.2.2, running only the following let's believe we don't host the client anymore:

# dig DOMAIN_NAME
results : 1.1.1.1

Instead, it should do:

# dig DOMAIN_NAME
results : 1.1.1.1

# dig -t MX DOMAIN_NAME
results : mx.domain.server

# dig mx.domain.server
results : 2.2.2.2

It would then consider we are hosting the emails for that domain since 2.2.2.2 is part of the servers assigned IPs. It's not perfect .... but a bit more accurate. As we are now seeing a lot of accounts highligted in red that DO have services on our servers.

This would indicate that the client still has some service running on our servers. Instad