I have a contact list of 55 names that I use to send out a weekly report using the bcc feature. Over the last few weeks not everyone has received my mails although I do not get any delivery failure notifications.
My "sent" copy usually lists all the bcc names but today's shows just 5.
Sorry you are having problems sending BCC email. Just to be certain we are talking about online webmail and not a client? If so I have just tried it on one of our email addresses here with a large BCC list and it seems to be working. I wonder if that particular contact list has become corrupt. Do you have any other contact lists to try, perhaps it is worth creating another one to see how that goes although apologies for the work involved.