On RECEIVED emails, you cannot. BCC stands for BLIND Carbon Copy, the whole point being, recipients cannot view who the email was also sent to.
As for email YOU SENT, you could check the full headers of the email in your sent folder, but I'm sure you'd already know who you sent the email to so doubt this is what you want.
If you want to send an email to multiple people and want them to be able to see the other recipients, us CC, not BCC.
