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.
I was just about to submit this same bug. I noticed it when I sent my VarAC Wednesday email and I got four copies of it at varacwednesday@gmail.com. I also got 4 copies sent to my personal email address I'd added with a comma. I copied the message out of the SENT folder and resent it via another Gateway and only got one message in both locations. We receive a large number of duplicate check-ins to VarAC Wednesday and I assumed it was because people were still learning and that may be true as well. Looking through today's check-ins, I see a number of duplicate check-ins that all appear to have been sent at the same exact time -- suggesting it was one email that was repeatedly sent. Here's my guess. So far, every one of these has had two destinations in the TO: line -- varacwednesday@gmail.com, (their personal email). My email was a Yahoo account and I've seen gmail accounts as well. The problem is, as Irad notes, creating a repeatable test case may be hard or impossible if it has something to do with the timing of how a gateway handles an email with two destinations. Or I may be wrong entirely. Edit: I originally said I only got 3 copies in the my personal email. The 4th was in the spam folder.
Originally, I thought he did it, see https://www.varac-hamradio.com/forum/bug-reports/check-for-illegal-email-names-or-addressees-v12-0-4
But it turns out that I was wrong, and VarAC 12.0.4 did it, but itself. Not user error.
I apologize but I was not able to duplicate it.
There is no way to enter this format as a valid email:
iradirad@gmail.com<iradirad@gmail.com>
unless I did not understand