I have a question about the error description in the Communication History screen.

We are using MailGun as email service. We normally don't see INTERNAL SERVER ERROR as a Note for the Failed reason, but just this past week we had a communication with around 50 of these errors. I checked the Exception List within Rock but didn't find any errors relating to this. 

Is this something we will need to check on Mailgun side? More importantly, it seems like Communication failed this way wasn't retried, wondering if anyone has experienced this with Mailgun before and know of a good way to either be alerted to remedy this error.

Thank you.