450 [SMTP Proxy] Temporary denial of connection for Zombie matches - Unable to receive emails on Exchange server 2003 Sp2

Symptom:

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1. Unable to receive mails from certain domains -

2. The sender recevies and NDR with the description "450 [SMTP Proxy] Temporary denial of connection for Zombie matches"

3. The message probably is not sent through Exchange Server

Cause

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Trend Micro InterScan™ Gateway Security Appliance or Similar device

Resolution:

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Disable the device, it should allow mails

--> if the mail is legitimate then they should get in touch with Trend Micro or any third party

Resource:

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https://us.trendmicro.com/us/products/mb/interscan-gateway-security-appliance/

Courtesy Ketan Thakkar