[imp] mail.yahoo-esque "Block HTML graphics in email messages from being downloaded" functionality?

[Liam Hoekenga]

Why would I want to prevent HTML graphics from being downloaded? 
We just got a piece of feeback re: our IMP installation - they're worried about
SPAMmers  being able to track active email addresses by image links in HTML
email they've received.

Apparently, Yahoo just added the ability to turn off "img src" tags in HTML
email (letting you turn it back on per-message when you think the message is safe).

Would it be worthwhile considering adding similar functionality to IMP?  

I've attached Yahoo's help text about the feature.
Liam

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from http://help.yahoo.com/help/us/mail/context/context-71.html :

Emails can contain offensive images or can contain invisible images that tell
the sender that you have opened that email (and thus verify that your email
address is active).  To prevent spammers from subjecting you to these images,
you may wish to prevent all images from loading until you are satisfied that
they are safe to view.  This is one of the many ways Yahoo! Mail protects you
from spam. 

By enabling the option to "Block HTML graphics in email messages from being
downloaded," all remotely stored images will be replaced with this image .  To
view the message with the original images, click the "Show HTML Graphics" link
at the bottom of the message. 

Why do I still see images in Yahoo! Mail? 
Images that are sent as attachments will be shown in the attachments area, even
with this option turned on.  Also note that this option will not prevent images
outside of the email messages from loading.  Navigational, informational, and
advertising images will still be loaded. 

If this is not what you needed to know, check out our Online Help Desk.  Visit
it any time by logging into your Yahoo! Mail account and clicking on the "Help"
link located in the upper right-hand corner.