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Undisclosed recipients may be available in the headers of the sent email, or it may be hidden.

I understand "undisclosed recipients" being blocked from the person receiving the message, but is there a way to find out who I sent a message to that shows only undisclosed recipients? I'm using Thunderbird and Gmail.

In this excerpt from Answercast #27, I look at the way various email programs either reveal or hide a list of undisclosed recipients.

Undisclosed recipients

I honestly don't know about both Thunderbird or Gmail. It really varies depending on the program.

The thing to do is actually very simple. Go to the Sent mail folder in your email program. In the Sent mail folder, open up one of the messages that you had bcc'ed recipients on.

Look at the headers

Make sure that all of the headers are visible. I know that Thunderbird only shows a subset of the available headers by default. You may need to look at All Headers. Or you could even use Thunderbird's View Source option to take a look at the actual source for the message.

It is very possible that the email program will show you exactly who the message was bcc'ed to – who the undisclosed recipients were.

Sometimes, it's hidden

Unfortunately, it's also equally possible that the information is not there.

Many email programs simply strip that information off before it is actually placed in your sent mail. In other words, there's no way to find out who you bcc'ed on an outgoing email in some email programs.

The bottom line is to simply take a look at the message in your Sent folder. If the information is there, it should be displayed.

End of Answercast #27. Back to – Audio Segment

Article C5487 - June 18, 2012 « »

Leo Leo A. Notenboom has been playing with computers since he was required to take a programming class in 1976. An 18 year career as a programmer at Microsoft soon followed. After "retiring" in 2001, Leo started Ask Leo! in 2003 as a place for answers to common computer and technical questions. More about Leo.

Not what you needed?

June 19, 2012 9:42 AM

A friend of mine {email address removed} has a very hard time of late, he cannot send attachments because they get stripped after leaving his computer . Any help?

John Servis
June 19, 2012 6:49 PM

I've been sending email to friends for years. Now I'm confused. What are " undisclosed recipients"? i thought email only goes to the people or person you send it to? Why would it go anywhere else? and to who?

Mark J
June 20, 2012 12:31 AM

When sending an email, if you put an email address in the BCC field instead of the To: or CC: fields, any reference to that email address are stripped from that email when it is sent. In other words, BCC: means the other recipients of that same email don't know who else received it.

June 22, 2012 8:34 AM

I don't think the article mentions it, but BCC means "Blind Carbon Copy".

When you CC someone, everyone in the TO: and CC: fields get to see all the other email addresses in the TO: and CC: fields. Makes sense, nothing is hidden. The normal situation is: all your recipients get to see whom you sent your email to.

But when you BCC someone, no one in the TO: and CC: fields gets to see the email addresses who've been BCC'd. So, the BCC addresses remain hidden to the other recipients. It's a bit sneaky, sure, but it has many legitimate uses.

The problem Leo is addressing is: sometimes you (the sender) forget whom you've BCC'd the email to, and unless your Sent folder saves the BCC list (some don't do this), there may be no way of going back to a previously sent email and finding the BCC recipients.

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