Teach your staff about BCC

Every now and then I'll get an email from someone that's been addressed to a number of people. I can tell how many and who they are because all of our email addresses are listed in the "To:" header. My email address has been sent to a list of people I don't know.

There are a couple of reasons I don't want my email address broadcast to the world.

Spam et. al.

I often don't know many of the other people on the list, and more to the point, I don't know anything about their computers. It's possible, probably likely, that in an email addressed to 20 people, at least one of them has a fairly insecure computer and probably has at least one virus or a trojan. When the insecure computer receives the email, my email address going to be visible to this malware.

In short, I can have the best and most robust security on my computer, and I can ensure my email address is never published on the web, but all of this is useless if a single person sends my email address to a compromised machine.

Email addresses can be personal

I may be in the minority here, but I maintain a large number of email addresses. Having my own domains means that I can set up separate email addresses for job applications, friends and family, work, web enquiries, and so on. Right now, off the top of my head, I can think of about twenty email addresses that I use regularly. Most are simply forwarders, but they allow me to categorise incoming emails efficiently.

The other thing this lets me do is control communication. If I am wary about giving a company or a person my email address, I'll create a new one. If I start getting emails I don't want, or if for some reason I don't want them to contact me any more, I can delete the email address.

Now you can see the dilemma. If I've given a particular email address to one company and they broadcast it to other people in a group email, I lose control.

Easily Fixed

If you're reading this blog, I'd be surprised if you didn't know about BCC, but I'll summarise just in case.

When sending an email, you can put recipients' email addresses into the "To:" field, the "CC:" field, or the "BCC:" field. "To:" and "CC:" behave the same, but "CC:" indicates that the person is being given a "carbon copy" - a legacy name from the paper days.

"BCC:" stands for "blind carbon copy". These people will still receive the email, but the email addresses in this section will not be included in the header. They will be kept private.

The problem of sending everyone's email addresses out with the email is obviously easily fixed. Just put all the email addresses in the "BCC:" section. For emails amongst groups of friends and family, it's often not a big deal, but in business it's frankly unprofessional.

Design flaw

People still don't know about BCC. I sometimes feel compelled to educate the sender of a group email about BCC and the usual response is surprise. They usually aren't even aware of this function.

I think the problem is deeper than just a lack of education. There are fundamental design flaws here. Now, email is old - Wikipedia claims that it's been around since about 1965. So I'm not going to suggest any fundamental technical changes. Such changes would be infeasible in a system that a) works, and b) is older than the Internet.

A significant part of the problem is that it's called "BCC". What the hell does that mean to the average person? Even expanding it to "blind carbon copy" doesn't really help - it doesn't describe its behaviour.

"Carbon copy" is relatively easy to understand. It's at least reasonably clear that the people in this section will be getting a "copy" of the email - it's not directly addressed to them, but they'll see it anyway. But what does "blind" mean? That it will be invisible? It'll be transmitted in Braille? People won't know what BCC does until they're told.

The other problem I can see is that "BCC:" isn't presented as a default field in many email clients. The main email clients I use are Outlook and Gmail. In both cases, "BCC:" must be explicitly turned on.


  1. Change the name. "BCC" doesn't mean anything - even when it's expanded to "blind carbon copy" it doesn't mean anything. Obviously, this change can't be fundamental, but it can be cosmetic. If an email client changed "BCC:" to "Discreetly To:" or something similar, it might help with people's understanding.
  2. Change the behaviour. In an office environment, group emails to external domains should, by default, include everyone in the "BCC:" field rather than the "To:" field. If that's too extreme, it should prompt the user, suggesting that perhaps they don't want to share the list of email addresses with all the recipients. At the very least, hiding email addresses from the other recipients should be a very visible option.
In the meantime? Teach your staff about BCC. Make sure they use it when it's appropriate.


Damian Brady

I'm an Australian developer, speaker, and author specialising in DevOps, MLOps, developer process, and software architecture. I love Azure DevOps, GitHub Actions, and reducing process waste.