"Sender Domain Not Found" means that Email Security cannot retrieve the DNS A record or Mail Exchange record for the sender domain.

To resolve the issue, follow these steps:

1. Add the email sender to the Approved Sender's List
   • To add the sender, follow: Manage the end user's personal Blocked/Approved Senders list in the End User Console (EUC) in Trend Micro Email Security (TMEMS)
2. Enable Unknown sender domain check under Sender Filter settings.
   1. Login to your Trend Micro Email Security console.
   2. Go to Inbound Protection > Sender Filter > Settings

      

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3. Tick the checkbox to enable Unknown sender domain check under Settings for Approved Senders.

   

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