问题
When an Auto-Reply Message is generated by Gmail for a message, the auto-reply message is not Threaded like a normal reply and the auto-reply message does not contain In-Reply-To: and References: header in its Headers Payload. The ThreadID of the auto-reply is different than its original message (unlike a normal reply where ThreadID remains same) Which logic should we use to co-relate an auto-reply to its original message? In Other words, how do we figure out to which message is an auto-reply for?
Using Gmail API
回答1:
There will be a portion of the subject of the auto-reply that matches the subject of the received email. Also, the timestamp will be close but later than the timestamp of the received email. It's not perfect, but should be functional.
来源：https://stackoverflow.com/questions/48635709/auto-replies-to-an-email-from-gmail-dont-have-in-reply-to-and-references-h