I have been able to cut and paste relatively non-formatted email address lists into the bcc fields before, but I can't remember the exact procedure I used. I think I was able to copy a column of email addresses and simply press ctrl+V in the Bcc field in Outlook once.

Another time, I pasted them into Notepad first to turn them into straight text before pasting into Outlooks BCC field, but I'm really not sure that step is necessary.

Also be aware that different email providers set different limits on the number of names you can have in a BCC. GoDaddy is high at 99. Others might be 50 or so.