blind carbon not showing in sent folder - XFinity

I sent a message to 60 people yesterday as Blind Carbon.

Today, I wanted to review those I sent it to, but the message is not showing up in my Sent Folder. Other emails I've sent before and after this message do show up, but these are typical emails sent normally and to one or a few individuals only.

Can you tell me why I can't see the 60 I sent my message to, in my Sent Folder?