The list of BCC’ed recipients is not included with emails, so there is no way of determining if or who else the email was sent to.
While there are settings and services that claim to be able to determine if an email has been opened, they are notoriously unreliable and pointless.
Once you hit that Send button, you must assume that there is no way to stop your email from being sent … even if it’s to the wrong person.
Email programs commonly block remote images. I’ll look at why, and how spammers and others use remote images for good and evil.
Often images are used by newsletter providers to track how often emails are read. Yes it’s tracking… but is it something you need to worry about?
In a work environment all bets are off. If they’re looking hard enough, an employer can see everything you do on a work computer.
It is not reliably possible to determine if an email has been read or opened. They keyword there is reliably. There are techniques that get some information, but it’s impossible to be 100% accurate.
So much information in email can be spoofed that it’s difficult to prove where an email came from unless you look at the headers.
This is a frustrating situation that happens regularly to businesses running email lists. More than likely someone on your list is automatically forwarding. There is one way you may be able to track down the source.
A web “beacon” or “bug” is simply something in an email that reports back to the sender that you’ve opened the mail.