SpamSieve fails to identify spam when the email contains an attached image. Moreover, in such cases, it fails to even log the email in SpamSieve Log.log. If no attachment is present, SpamSieve works properly. Also, SpamSieve always works properly in Apple Mail on the same machine.
Steps I have taken to try to fix the issue:
Uninstalling/re-installing SpamSieve
Systematically trying all options in Outlook Preferences -> Reading -> “Automatically download pictures from the internet:”
None of the above have fixed the problem. Your advice is much welcome.
You are running into a bug in Outlook. If you send me an e-mail, I can get you a pre-release version of SpamSieve that tries to work around this problem.