Welcome to the Auth0 Community!
A couple of housekeeping items; If you reply to your own thread, it knocks it out of the unanswered queue. Try the edit function if you need to add info to your post.
Additionally, if you need urgent/time-sensitive support, all of our paid plans include dedicated support. No need to @mention our team directly, please be patient while we get to your topic!
As for your issue:
If it is working for one email client, but not another, that would suggest the client is the source of the issue. Are the emails making it to SES? This would confirm that suspicion.
Have you looked to see if the emails are being quarantined?