Hi @Linda Gonzalez ,
Welcome to our forum!
I was wondering if the "you are not responding to the latest message" option could appear also if someone Who was not included in the original chain opens the email saved.
Based on my test, after user A is add in a conversation, when some emails are received, if user A is going to reply the non-latest email, he will get the "You are not responding to the lates message in this conversation. Click here to open it" reminder on the top of the email.
Hope to help you!
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