- The email did not reach HES/HES - Inbound Filtering.
- Trend Micro's ERS databases include the IP address of the sending MTA and the searched recipient is not the first recipient during the SMTP handshake.
For example, firstname.lastname@example.org sent the email to email@example.com and firstname.lastname@example.org. In this situation, HES / HES - Inbound Filtering will return a 550 or 450 error after the first RCPT TO and will only log email@example.com in the mail tracking database. HEs / HES - Inbound Filtering' actions prevent the second RCPT TO from happening and the logging of the second email address.
- Search for the email address of the sender to determine if ERS blocked the sender.
- If ERS did not block the sender, add the email address of the recipient to make the query more specific.