I saw this question: Is there any way to make Gmail automatically delete out-of-office replies from cc addresses? where Thor84no was unhappy to receive out-of-office emails from people he added in cc in his sent emails.
My question is related to the receiver: if Thor sends me an email in Cc and I'm out-of-office, does my responder reply to him and to all the other addresses in that email he Cced?
I know this wouldn't make any sense, but I just need to confirm, the only thing I found from Gmail was:
Messages classified as spam and messages addressed to a mailing list you subscribe to will not receive a vacation response.
Best Answer
auto-replies will only be sent once to each address that messages are received from (with a proviso about about messages sent four or more days apart).
Whether addressed to you directly ("To") or copied to you ("Cc") in your example it is Thor84no who has sent you the mail, so Thor84no from whom the message was received and hence Thor84no (and only Thor84no) to whom the vacation response is sent.
The alternative, that fellow recipients are also sent the out of office notification, could have interesting repercussions where there are many addresses in Thor84no's choice for the Cc/Bcc list and a number of them also on holiday at the time and with their vacation responder behaving in the same way.