The code here: http://dxr.mozilla.org/comm-central/source/mailnews/base/src/nsMsgStatusFeedback.cpp#120 never runs since OnStateChange gets a uri for the inline image (1 if there are > 1) and not the original uri. And the image uri doesn't have a msgWindow, like the original uri does. so this code never runs: http://dxr.mozilla.org/comm-central/source/mail/base/content/msgHdrViewOverlay.js#668 one result being that images never get sized right (in something like alt.binaries.birds). Bug 193317 removed the ability to get the originalUri for nntp; it's possible the change there is no longer relevant, and there's awareness this may not be a good idea. A possible fix is to revert that change and get the originalUri from the channel in OnStateChange. (Imap has a tangle of notifications different from nntp though it seems parts of imap were copied into nntp). Attached is a nonworking wip debug patch, in case someone ever comes this way again.