MX record does not exist
HES checks if the recipient domain has a valid MX record to deliver the email. If the MX record does not exist, the email will be rejected.
To query, open a command prompt and then type "nslookup -q=MX domainname" where "domainname" is the domain that you want to query.
The entry below shows that HES rejected the mail:
To resolve the issue, the administrator of the domain should correct the DNS record.
The sending IP is a spam source
Some emails are rejected because the sending IP is a spam source. Under Mail Tracking, the entries for rejected IPs in some cases say Real-time Blackhole List (RBL) or Quick IP List (QIL).
You can check if an IP is listed through the Email Reputation Services (ERS) website. In case your IP is listed, you can file a removal request from the ERS site.
If you are the administrator, you can approve or block IPs in the console under IP Reputation > Appoved/Blocked.
The recipient's address is not in the current directory
The directory management feature is enabled however the receipient's address is not in the directory. For more information on the directory management feature, refer to the following topic: About Directory Management.
IP Reputation settings
The IP Reputation settings could be the reason why the email is rejected. For more information, refer to the following topic: IP Reputation Order of Evaluation.
If the issue persists, submit an online case to Trend Micro Technical Support. Kindly include the following information:
- HES login ID
- Activation Code
- Mail tracking logs - Include a screenshot and information about the email(s) including the sender, recipient, timestamp, and IP address.