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We frequently receive emails from unknown sources as well as know sources that seem to be malcious. Is there a way I can peek at the message headers without actually clicking on the email message or opening it? We are using the latest version of Thunderbird and use both IMAP and POP3.

Is there also a way to filter emails via message headers?

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Which headers to you want to view? Opening an email isn't likely to cause an issue, particularly with Thunderbird. – Paul Nov 15 '11 at 22:25
@Paul - All headers available to be viewed. Not sure there are different headers. If so what are they? – PeanutsMonkey Nov 16 '11 at 0:49
up vote 2 down vote accepted

For IMAP there does not appear to be a way of reading the headers only.

For POP3, you can choose to "Fetch Headers Only" which will mean that the body of the email remains on the server until you explicitly request it to be downloaded.

For filtering, you can create rules based on any header you like. Go to

Tools /  Message Filters... / New...

Choose a name for the filter, then in the filter criteria dropdown box (which defaults to Subject) choose Customise...

Here you can add a custom message header that can be used in filters. For example, you can add


And close the dialog, then this will appear as a filter option in the dropdown. Thunderbird will look for the header in emails when processing filters, and if it matches the criteria, will carry out the filter action.

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Thanks. Does that mean I would not be able to read headers from an IMAP server unless I click on the email and then attempt to view headers? – PeanutsMonkey Nov 16 '11 at 6:17
Yeah, which would require you to open it and tb will download the entire message - I can't see how you can achieve what you want with thunderbird – Paul Nov 16 '11 at 7:44
Which clients would support what I would like to do? – PeanutsMonkey Nov 17 '11 at 22:33

I know it's a bit old, but I stumpled over this thread while basically searching for the same. I was used to be able to right-click an email and select "View Source" from Windows Live Mail, but Thunderbird is not that straightforward. Instead:

Select email in list -> Options Menu -> View -> Message Source

Since this is a bit inconvenient to do for every email, use the hotkey:

Ctrl + U

I think this was already possible with the Thunderbird version from Nov 2011.

Sorry, but I have to leave this rant here: why does open-source-software so often come up with so inconvenient ways for simple tasks. It really suppresses a smooth experience. I use this feature so often, I think I have to revert back to Live Mail or maybe even better Outlook. Those just work™.

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