Edit: We have released a fix for this issue, all of the error mail should now be back to normal. If you claimed your mail while it was in the 'error' state, you can contact customer support. I'm told that they are not able to replace the exact rewards, as they are not able to send specific runes as compensation, but they will look at your account to confirm your leaderboard standing and mail claim situation and give comparable compensation.
We are aware of an issue that has caused mail from the Jerry Boss event to become "Error" mail.
Please do NOT delete this mail. We are currently looking into a fix that will repair the mail without it having to be resent. If you delete the mail, we cannot guarantee that you will be able to get your rewards.
Joel | Community Manager | Boss Fight Entertainment