Hi MeriLu,
Sorry for the delayed answer, i did some testing and i was able to replicate your issue, them i've searched internally for a solution.
For now, unfortunately there is nothing to be done about it, i'd recommend you to the best configuration on your email to avoid those emails coming from your TRB141 to go to the spam.
But in the upcoming firmware version 7.3, there will be a option for setting custom headers in those emails, and with that, it will be possible to reduce the spam rating and possibly solve this issue.
Best regards.