"Cannot find mail recipient" error

So tonight was a big night for my guild as I put a reward for a progression fight. We successfully killed the boss we set our goals toward, and the reward was 1500g per person. Since the raid disbanded I have told them I will be mailing out all of the gold to everyone's characters that participated for it.


I was able to successfully mail 22 out of the 24 raiders with no error. Simply the mail was:

To: <raider's name>
Subject: Putricide Bounty

Amount to send: 1500g



there were no messages attached and 22 mails went out perfectly fine, until the 23rd where I began to get the error "Cannot find mail recipient" error. I am spelling the name correctly (in addition, the character I am sending it to is in my guild so the in-game automatic word completion function shows it). I am not running any mail addons as well.

Is this a new bug? or is this some type of warning or Blizzard security function?
I was just wondering why this was happening , or what may have triggered it. I have logged in and out, reloaded WoW, and reloaded my UI as well.