Also be sure that you send it from the email associated with your account. As per the update on the situation discord gave, in which it announced an extended deadline of 90 days up from 30 days from April 15th or account creation, the contents of the email don't seem to matter much.
I included my account userid and username just to be safe.
In email terms, a bounceback is a category of error that in this case meant that the email address didn't exist. Although, that's because I emailed opt-out instead of arbitration-opt-out. My mistake. After fixing it, it went through without a reply as has been the general experience.
I'm glad I'm not the only one. I'm not using the application until I get a response. For all I know, they may respond on the very last day or not respond whatsoever.