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In Thunderbird, because it sometimes stupidly does this thing where when I forward emails, the To or CC/BCC boxes just can't be selected at all. (I think it's an extension causing it but it didn't used to, only now that TB's updated more recently...)

It was an important domain registration email with password and logins in it!

I'm only asking because I'm paranoid (but also interested) - it didn't actually go to anyone did it? like the original sender or the email maybe? What happens when this happens - I haven't received any 'undelivered' mail server message back yet.


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up vote 0 down vote accepted

Open the sent mail headers and inspect "TO" field. If there is no any actual recepients - do not worry about that. I don't think that this email can be sent at all. Maybe this mail still in the outbox folder?

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Ah I see why it sent now. I have an auto BCC thing going in tb (either extension or mail rule,ages ago that I set it up), so the email sent to myself in BCC'ing, and again the TO filed says "undisclosed-recipients:;" which appears to be nobody, phew. Thanks. – user78017 Apr 7 '12 at 11:55
@crea7or: "undisclosed recipients" mails are definitively sent. – jlliagre Apr 7 '12 at 12:45

When you send mail with neither "TO" or "CC" field set but with a "BCC" one, your mail is displayed as being directed to "undisclosed-recipients". If you have inadvertently set the BCC to some valid external email address(es), the mail will be sent to them and you'll have no trivial way I'm aware of to know what these addresses were.

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