Fix the Autoresponder Function under IMAP settings
Autoresponder doesn't work under IMAP. You've to force the email out. I don't know if this would be a problem if there was an Autoresponder folder, like Inbox and Sent. With the world as it is, I would have though having a folder that contained all the sent autoresponder emails would be a given. This was you can see what autoresponders have been sent, and have proof that "at least" the message was sent.
Whether as a sub folder of sent items, or a folder in its own right.

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