How does using BCC help reduce spam?

The scenario works like this: you get a wonderful piece of humor via email - maybe a joke, some goofy pictures, or something else that you want to forward to your friends. (Note: never forward anything that actually asks you to forward it without checking it out first. It's likely an urban legend.)

The mail you got looks something like this:

From: yourfriend@reallybigbookstore.com
To: you@reallybigbookstore.com
Cc: anotherfriend@reallybigbookstore.com, anotherfriend2@reallybigbookstore.com,
    someoneelse@reallybigbookstore.com, acontact@somerandomservice.com,
    morepeople@somerandomservice.com
Subject: This is funny

I thought this joke was kinda funny:

A pirate walked into a bar and the bartender said, ...

(All the email addresses are fake, and just for example purposes.)

Your friend has emailed you some humor, and cc'd a number of other people.

Think about that for a moment. You can see all the email addresses on the CC line. If you're a spammer, you just got 5 more known-valid email addresses that you can add to your list of email addresses to spam. In fact, any of the people on the CC line could do this as well.

But it gets worse. You think this joke is really funny, and worth forwarding on to more of your friends, so you hit "Forward", and create a message that looks like this:

From: you@reallybigbookstore.com
To: aclosefriend@reallybigbookstore.com, familymember@somerandomservice.com,
    apal@somerandomservice.com, collegue@reallybigbookstore.com
Subject: FW: This is funny

Pretty cute...

> From: yourfriend@reallybigbookstore.com
> To: you@reallybigbookstore.com
> Cc: anotherfriend@reallybigbookstore.com, anotherfriend2@reallybigbookstore.com,
>     someoneelse@reallybigbookstore.com, acontact@somerandomservice.com,
>     morepeople@somerandomservice.com
> Subject: This is funny
> 
> I thought this joke was kinda funny:
> 
> A pirate walked into a bar and the bartender said, ...

Just look at all the email addresses that are visible to anyone who gets this message. It's a veritable gold mine of known-good email addresses that they can then use for any purpose they wish. Spam, of course, is the most obvious, but there are a raft of privacy issues that result as well.

And after the message has been forwarded a few times the list of juicy email addresses at the top often exceeds the length of the actual message at the bottom!

(And you'd be surprised at how often the resulting email messages gets forwarded by someone to a mailing list that is archived on the web, where it a) lives pretty much forever, and b) is even more easily harvested by spammers.)

There are two things you must do to avoid adding to the problem:

• Use BCC for the recipients. This will prevent the email addresses you send the humor to from being visible to the people that get it. (How you do this will vary from mail program to mail program, but almost all have it.)

• Edit out any email addresses in the body of the message before you send. This will remove all the prior recipients from being visible, and has the added benefit of making the email easier to read.

Of course you should always consider whether the message should be forwarded at all, but I'll assume you've made that decision properly.

So this time, when we forward that original, we do those two things:

1. Instead of entering all those addresses on the TO or CC lines, we send the message "to" ourselves, and put all the recipients on the BCC line.

2. After pressing the "Forward" button, but before pressing "Send", click in the body of the message and simply delete all the lines that are nothing more than forwarded email headers.

Using the example from above, here's the result:

From: you@reallybigbookstore.com
To: you@reallybigbookstore.com
Bcc: aclosefriend@reallybigbookstore.com, familymember@somerandomservice.com,
    apal@somerandomservice.com, collegue@reallybigbookstore.com
Subject: FW: This is funny

Pretty cute...

> I thought this joke was kinda funny:
> 
> A pirate walked into a bar and the bartender said, ...

What the people getting this message see is this:

From: you@reallybigbookstore.com
To: you@reallybigbookstore.com
Subject: FW: This is funny

Pretty cute...

> I thought this joke was kinda funny:
> 
> A pirate walked into a bar and the bartender said, ...

Not an email address to be found.

Nothing for spammers to harvest.