Is there a max # of emails that xenforo can process per second through SMTP? My max send rate is 28 per second through Amazon SES and I'm trying to decide if that's sufficient or not.
SES will allow you to exceed that limit in short bursts, just not for a sustained period of time. If you do get throttled, I believe an error will be returned and get logged in the server error log. If necessary, getting a limit increase from AWS support is typically pretty easy.