Non-Delivery Receipts (NDRs) for emails rejected by Recipient Filter - Trend Micro Email Security (TMES) + Hosted Email Security (HES)

- Updated:
- 12 Feb 2021
- Product/Version:
- Hosted Email Security All
- Trend Micro Email Security All
- Platform:
- Not Applicable N/A

Summary

In TMES and HES when Inbound Protection -> Connection Filtering -> Recipient Filter is enabled, emails for non-existent users do not generate NDRs

Details

During the SMTP connection between the sender’s mail server and the TMES or HES mail servers, Inbound Protection -> Recipient Filter sends an SMTP Error back to the sender’s mail server instead of an NDR. It is up to the sender’s mail server to send an NDR back to the sender.

Example of an SMTP error:

Apr 18 21:55:22 in01 postfix/smtpd[52897]: NOQUEUE: reject: RCPT from unknown[undisclosed IP Address]: 554 5.7.1 <undisclosed recipient email address>: Recipient address rejected: Access denied; from=< undisclosed sender’s email address > to=< undisclosed recipient email address > proto=SMTP helo=<p1186-ipbf206oxxxx.xxxxx.domain.com >