How do I trace where a message originated

[Mannga]

Morning All,

I have been checking through the admin email box and have noticed that about 200 messages are arriving in the admin box with the following details

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A mail message was not sent due to a protocol error.

554 delivery error: dd This user doesn't have a yahoo.com account (lsdsgsdsiio@yahoo.com) [0] - mta161.mail.scd.yahoo.com
The message that caused this notification was:

To: <lsdsgsdsiio@yahoo.com>
From: <>
Subject: Undeliverable: re: video samples attached 8877006 9221TkQe6-784SUjL15-18
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How would I find out who sent this message?
Or how do I stop anyone sending anonymous messages through my email server?

Thanks,
Gavin