Ditto here, no further information at SendGrid for me. We were sending 400 emails in 30 mins on one list and 1600 over 2 hours on another, doing so without issue for two months. For the past two days, it is sending like one email every 5 minutes. The only notice in Status is that the email sending is slow. Just signed up for Premium to get an answer here. Not sure what else to do.