Hi @Jose IT Junior ,
I tested the phenomenon you described in the environment, the same problem occurred. You may want to achieve such an effect, but Exchange can not do it at the moment.
Example:
From: pepe
To: pipo
100100100
Signature.
From: pepe
To: pipo
100100100
Signature.
After reviewing the Microsoft documentation, I unfortunately told you that it might be a product design problem.
You can refer to the documentation:
https://learn.microsoft.com/en-us/exchange/policy-and-compliance/mail-flow-rules/signatures?view=exchserver-2019&viewFallbackFrom=exchsever%3D2019
If you do not want to receive duplicate signatures, you can add an exception that contains the content of the signature and your signature will no longer appear in the message you reply to. This may not be possible if you want one piece of content to one signature. There are also ways to add signatures from outlook, which you can also refer to:
https://o365hq.com/blog/how-to-add-email-signatures-in-exchange-online-microsoft-365-office-365/
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