Continuing the discussion from Any way to prevent notifications for post merges, moves?:
I don’t know if there is any way to resolve this but would be interested in knowing what others have done beyond training. Basically what is happening is that gmail is remembering discourse email addresses, which then are provided as autocomplete options the next time users write an email destined for the forum. Their post then gets added to the existing topic instead of a new topic. It’s happened a few times already.
Worse, it is also remembering discourse email address for users. So if you are not paying attention you can find yourself sending an email to discourse instead of to the person directly.