Outlook hangs on emails that have images with invalid network paths

At first I thought this could be an isolated problem, but several email from different sources are presenting the same problem. Whenever the email contains an (AFAIK malformed) youtube thumbnail URI, outlook 2010 (14.0.6112.5000 x64) hangs with this dialog on the foreground

The offending source code is

Interestingly enough, this image displays fine when viewed via webmail (google apps).

1. Shouldn't out look treat this link just like any other broken link and not hang ?


2. Why does the URI work on webmail but not for outlook?


3. Any suggestions on a temporary workaround?

Answer

This is a bug in Outlook (prior to and including 2010), as documented here. When an image points to a non-existing network share* (instead of a web server), Outlook’s “Internet picture blocking” functionality doesn’t kick in and Outlook still tries to retrieve the content in a foreground thread, which causes it to stall for about 1 minute.

*While the URLs that begin with // are simply protocol relative URLs, some email clients (Outlook especially, as usual) won’t try to use HTTP or HTTPS as the protocol. Instead they’ll use the file:// protocol and assume the resource you’re referring to is on the local machine (hence Outlook thinking it is a non-existing network share).

UPDATE: a few years later, a hotfix can be downloaded here, though it doesn't seem to always work in my case.

Bottom line: its not safe to use protocol relative URL in email.