Unable to receive email from certain domains

You may encounter cases where you are unable to receive emails from certain email addresses / domains. This can be cause for concern especially if you are waiting for important mail from old or new clients. First check that there are no technical issues with your LAN / router or office set up, and also check that the sender has no technical issues as well.

After checking that there is no other technical issue on recipient side and sender side, check the PTR settings and reverse DNS lookup of sender's server. Those with no PTR or reverse DNS are rejected by WWW.COM.PH's server. This is an anti-spam setting.

To check the reverse DNS, you can follow this simple step:

1. Go to www.dnsstuff.com
2. Scroll down to "IP Tests" and look for the Reverse DNS Lookup field
3. Enter either the IP address or domain name (without the "www") in the appropriate field and click the RevDNS button.

In the results field, you will be able to see if the target server has a PTR defined or not.

PTR assigns a name to the IP address. So if a recipient server only sees the IP address of the sender's server, incoming email from that server is classified as spam. The point of action needs to be taken by the system administrator overseeing the sender's email server.

As more and more servers start defining their PTR settings, they also start rejecting email coming from servers that do not have PTR settings. It is one way to combat spam hence the burden of responsibility is with the sender's server to comply with such settings.