I've been having this issue with Zukki-dar.
He's been sending this exact same mail (though the materials do change) every day, I'm not sure when it started but I believe it was shortly after the CwC update. I only get this issue on one character and that's the only hireling I have on that character. All of my other characters are unaffected, I'm having it on the PTS too, as well. I've tried contacting support about this in the past but didn't really get much help.