Everyone has seen an email that has been forwarded and forwarded so many times that you have to scroll down several pages to find the content. As you scrolled down, you no doubt saw dozens of names and email addresses of people who were included in earlier threads and who now are having their information shared with whoever receives the email next. This is not only inconsiderate, but opens these people up to spam, scams, and email from people they might not have cared to correspond with.
Whenever you want to send or forward an email to a group of people who don’t know each other, the proper etiquette is to put everyone’s email addresses on the Bcc: (or Blind Carbon Copy) line. This has the advantage of making your message look as if it were sent to each person individually. But more importantly, it keeps each of your contact’s email address private; no one else on the list, and no spammer, can see it.
In the past, criminals were just after e-mail addresses to spam or sell to other spammers. But now criminals also use the information about who your friends, and their friends, are to map your social network. Then, they send tailored spam, scams or phishes to you and a few of others in your social network because it makes the spam seem more legitimate. Consumers are far more likely to fall for a scam if a friend or family member is also on the "To:" line.
How to find the Bcc: Line
Every e-mail program has a Bcc: option.
Search in your e-mail program’s Help if you can’t find it readily. For example, for Microsoft Outlook you can find how to switch on your Bcc option here.
To protect your email from being bounced around and exposed to people you don’t know, you may want to include a message like the one below as part of your signature field at the bottom of your e-mail messages:
Note: To help protect my privacy, please do not expose my e-mail address to others. If you’re sending e-mail to a group that includes people I do not know, please put my e-mail address on the Bcc: line.
While a note like this is not likely can’t guarantee to stop your email from being shared with others, it will help raise awareness of the issue and should significantly reduce the frequency of your exposure.