Experimental for v5.0 Rated 5 out of 5 stars
Goto "view all versions" on the bottom of this add-on homepage.
Download the experimental version 1.2.1 dated 2011-07-01, 329.7 kB.
Works perfect with my v5.0 Thunderbird among about 30 other add-ons.
Display-Contact-Photo is perfect with intranet domain pictures to avoid wrong addressed extranet e-mails.