trouble delivering email role forwards to gmail

in #40585, we found that we specifically have trouble delivering "role" aliases (job-XX@tpo) to gmail.com addresses. the same user, sending the same mail, to individual users at gmail would work, but not to the role address.

i speculated that the problem was with the user identity on gmail's side:

https://support.google.com/mail/answer/22370

ie. that gmail is unhappy about receiving mail addressed to that job-direng@ alias because it doesn't know about it, but it's happy to receive (say) erin@torproject.org because that's the alias you have setup there?

could it just be that you need to setup the alias as documented above?

so one thing to check is to see if @isabela or @ewyatt could follow the above guide to see if it helps with the problem.

otherwise I'm hoping solutions considered as part of the larger "plan for email" project (#40363 (closed) and TPA-RFC-15) would help with this (specifically SRS but also possibly ARC?).