I want to send automated replies to emails I receive on my gmail account, if I haven't corresponded with the sender before. This basically mimics an out-of-office / vacation reply, but only triggers in case the sender is unknown to me.
From what I have seen in the settings of gmail, sending vacation replies to contacts is no problem. I can send such messages to everyone in my contact list, but it doesn't work the other way round.
If the solution requires me to add all whitelisted senders to my address book, this is OK, but I would prefer a solution that works based on my conversation history.