If emails are bouncing back from sender to external emails with the error message 'Recipient address rejected: NO-DOMAIN' where the message is rejected by: relay.hes.trendmicro.com or relay2.hes.trendmicro.com
, it is likely that the connector is still using the relay for HES, which is no longer active or has reached EOL (End of life). Any email that is relayed to HES will be rejected automatically.
To resolve this issue, remove the HES relay and use the TMES relay <domain>.relay.tmes-anz.trendmicro.com> for the Outbound connector to send an outbound email successfully.