Running PerplexMail in an IIS application

Hi,

I'm trying to run Umbraco with PerplexMail in an IIS Application (so, as a subdirectory of an existing Umraco site). After a few tweaks to the web.config (adding around system.web and system.webserver) and adding tot umbracosettings.config I'm getting the error "Could not load type 'PerplexMail.HttpStatisticsModule'. "

If I comment the lines in both system.web > httpmodules and system.webserver > modules the site works. But of course that means I can't use Perplex. So any ideas about how I can use Perplex in an IIS application-website?