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+If a message is sent through Gmail MSA the following happens:
+
+1. If similar message(*) exists in Sent Mail folder, then nothing is done
+2. If there is not similar messages in Sent Mail folder then the message submitted to MSA is copied to Sent Mail with Return-Path and Received header
+3. If IMAP client appends messages that have a similar message in the same folder, then the existing message is deleted and new one is appended resulting in *1234 EXPUNGE* + *1234 EXISTS*
+
+(*) similar message is a message with same Message-Id and additional fields (exact fields are not known). If the message does not look similar but has existing Message-ID then nothing is deleted. If Message-ID of the new message is unique but otherwise looks like existing message, then also nothing is deleted.
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