Akismet plugin does not seem to work properly with FS Contact Form, which supports spam filtering through Akismet. I submitted the same spam message via form and as a comment. Comment was blocked by Akismet as expected, but the message went through with the following line in the body:
Akismet Spam Check: passed
I contacted the author of FS Contact Form, Mike Challis, but he couldn't figure out why comments and messages are treated differently by Akismet. I hope that Akismet creators can help me to investigate this issue. I am using FS Contact Form v.2.9.6 and Akismet v.2.5.1.