I use claws on some machines (it has a different set of annoyances than Thunderbird) and it has the feature to pull senders&#x27; images from <a href="https:&#x2F;&#x2F;www.libravatar.org&#x2F;" rel="nofollow">https:&#x2F;&#x2F;www.libravatar.org&#x2F;</a> . The occasional mailing list participant gets an image that way and, amusingly, the occasional spammer as well.