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.Martin commented
For you looking for a work around, it's possible to do something on your own in powershell. By default, you won't recieve a NDR until 24 hours later. Instead, you can query those emails being pending due to the lack of TLS and pick them up and send a custom email to the sender. I just did this for my own organization as we have the same requirement due to GDPR.