Today, based on feedback, we’ve lowered the timeout to 24 hours. In the future, we are planning more improvements, although we do not have any dates or details to share at this time. Thank you for the continued feedback.Paul K commented
I can't believe this still isn't supported, I honestly thought after the EU regulation changes in 2018 that enough people would be screaming for this that it would have been made a priority. There's no excuse for the bounce to be after 48 hours with no warning to the sender until the queue expires. If the timer can't be changed then there should be a toggleable option for an instant bounce if the receiving server indicates STARTTLS not available.