I've edited out some of my info for obvious reasons. I get these emails at least 2-3x a week. They keep telling me to make sure the software (xenforo) is legit and up to date, and that my plugins are the official kind (noted - tiagachat - [bd] widget framework) ect, ect.
I suspect it has something to do with the alerts on the forum. These emails they send me all have been alerts I've seen, replies to forum posts, ect. I've taken the measure of having all my users disable their forum announcements. Trying to see if that may help.