New SBS 2011 installation is having trouble sending to Office 365 accounts.
Delivery is delayed to these recipients or groups:
This message hasn't been delivered yet. Delivery will continue to be attempted.
The server will keep trying to deliver this message for the next 1 days, 19 hours and 54 minutes. You'll be notified if the message can't be delivered by that time.
I know that at least 2 of these domains that bounce back are on Office365. I suspect that maybe more of them are as well.
I forgot to setup reverse DNS when I deployed, but that was rectified 5-6 days ago.
MXToolbox says that we're good other than a long transaction time. Not sure what's up with that. When I click for more information it doesn't give me much:
We were able to connect to your mail server on port 25, but the diagnostic session took longer than expected. This could indicate that your email server is under heavy load.
Here are the levels for which we issue warnings and alerts:
Over 5 Seconds: Warning
Over 8 Seconds: Alert
Having this warning on your lookup does not necessarily mean that you will have a problem receiving mail. It is simply a warning that things are less than optimal. This could end up causing users to experience delays with inbound mail.