You shouldn't touch it for more serious reasons. I can confirm with absolute certainty that Gmail occasionally silently drops mail you send. This does not seem

You shouldn't touch it for more serious reasons. I can confirm with absolute certainty that Gmail occasionally silently drops mail you send. This does not seem to be directly related to Google's anti-spam system, neither sender nor recipient are marked as spam originators in those cases, and the mail will not bounce back. It simply disappears.