I had a strange rejection several months ago too, and mailing support as to why it was rejected, the reply was it was an internal use address only. Rookie response from a frontline support person that didn’t know what they were talking about.
Pressed others further and they confirmed it was still a viable address. And, I finally did get a response which quoted the original mail, so I know it went through. I followed up with email through my MyTesla account, although it took weeks, not the two days they state it should take to get a reply.
Could also use
[email protected] I guess, but I’ve never used that one so can’t verify it’s still valid.