We use email communication for our help ticket systems and all our users were affected (~20k). At 9am it was ~10min delay. 10am about 21min noon about 1h 3p

We use email communication for our help ticket systems and all our users were affected (~20k). At 9am it was ~10min delay. 10am about 21min noon about 1h 3pm emails with ~3h delay arrived. Then it got better. We werent' able to help our users and they of course blamed that we responded slowly. Actually a bounce message would've been preferable since then they could've used a phone or stopped by. You don't really expect your company @example.org to take 3h. Either bounce withing ~3-4min or you expect it to be delivered by that time.