While snapshots were being purged service was running fine but after snapshots were purged we ran a ZFS scrub on the pool which caused the kernel to hang at boot at 12:30PM EST similar to this issue.
We have restored a backup from this morning at 5:41:13AM EDT.
Once the old VM is back up and running we will do a diff of the mailboxes directories and restore those files on the new VM.
Later this week we will schedule a window to do some filesystem maintenance to prevent this from happening again.