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The results will be returned in the frame below, it will include data of the last 50 messages of the conversation. The value 50 is the maximum, it can be reduced to any smaller value, like 10.
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To retrieve previous messages, you can copy the value returned in @odata.nextLink, copy it to the query box, and run the query.
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click on the link: Click here to follow the link.
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You can search within the returned results for your chat messages