I use eM Client 9.2.1222 and the mail server is Gmail.
I cannot delete a conversation (3 messages) in my inbox. I cannot move it either to another folder. In fact, I initially already moved it to a local folder and I see it there too. This is weird as I never had this problem before.
I do not get any error message. I just see that the messages are not deleted. It seems they will stay in my inbox for ever. The conversation does not appear anymore in the inbox of my iPhone.