Issue
M7SJO reports that his emails relayed through my station are duplicated - two copies of each email are sent.
It turns out that my VarAC station sends to his email address twice per email message.
VarAC is sending to "email <email>" i.e. VarAC is copying the email address and prepending it, which is in the position of the addressee name.
Gmail interprets this as an additional email address, and sends two copies to the addressee.
When he sends email through SM3ULU, this issue does not happen. The message is sent to only one addressee.
I am using VarAC v12.0.4. They are both using v12.0.0.
Originally, I thought it was an addressee + name validation issue on his end. (I submitted a bug report requesting to add validation.)
But after reviewing the Chat History it appears that VarAC is sending to "email <email>" i.e. VarAC is copying the email address and prepending it, which is in the position of the addressee name. And Gmail interprets this as an additional email address, and sends two copies to the addressee.
Chat History

I noticed this morning that the gateway KF0QQR <benjamin.arthaud@toasterlizard.net> always generates multiple emails. It's record was 14 today. Maybe there's a clue in there somewhere.