HTML msgs filtering

Good Day to all!

In my resource file, among others, I have:

<MIMEfilters>
text/html; m2h_text_html::filter; mhtxthtml.pl 
text/x-html; m2h_text_html::filter; mhtxthtml.pl
</MIMEfilters>

yet no HTML formated msg seems to get filtered.

I'm using NT4 /ActiveState Perl/Eudora 5.1 mailbox files and MHonarc 2.5.2. 

Is there anything one can do wrong or have I missed something in the Docs or, 
or, or?

I'd be thankfull for any good hint.

Happy Easter

Alex