Last night's Google outage is still causing shockwaves through some of their services. Gmail is sending back wrong bounce messages that say stuff like "email address doesn't exist" when in fact they do!
If you're getting a lot of bounce messages from OwnerRez today, please note that we are watching this and reactivating these email addresses for you.
When the smoke clears, please look at your Communication History > Email tab for emails that bounced and need to be re-sent. We do not have a mechanism for re-sending failed messages in bulk, so unfortunately you'll have to look at them and the ones that need to be resent one by one.