have you considered turning on the reading pane using F8 (It turns it off again as well) where you get all that information on the message header? No tool tip required

Hi Matt,

Thanks for the response and suggestion.

By opening Thunderbird's reading pane, and then clicking on an email message, Thunderbird opens the message, yes? I don't want to actually open messages from spammers thereby letting them know they've successfully spammed my valid email address - I just want to peek at what the actual From emaii address is without opening the email message, as shown in my original post's screenshot.

more misinformation and urban myths here than facts.

1. Thunderbird blocks remote images by default. 2. Thunderbird does not allow scripts in mail. If they are there they do not run. 3. The only link SPAMMERS or anybody in marketing gets to you is when you download their remote images, run scripts in the mail or click on links to go to their web sites. 4. When I or a spammer send a mail to say me@thinsplace.com. Most mail servers will refuse delivery unless the address exists on their server. 5. True spammers do not care if a large percentage of the mail they send is to dead email addresses and they make little or no effort to validate active addresses. Corporations like Walmart, Woolworths here in Australia, Ebay and Paypal are very interested.

With that knowledge, you are now aware that opening the mail tells a spammer nothing even in the remote chance they are interested.

Oh and the source of the urban myth is Microsoft whose mail clients allow scripting, remote images and uses the file extension of the file not it's mime type to determine how to open it.

That is the difference between a mail client where the developers think security first and one where the developers give the user what they want and try to tack on security after the fact.