WebMail sends mail messages without problem, except that attachments are not being sent.
If you have followed the instructions that WebMail gives in the error message (with regard to Internet Explorer settings) and you still cannot send attachments, then your computer and/or the computer which runs WorkgroupMail (if different) may be missing the correct DAO components.
Download the DAO components from Microsoft at http://www.microsoft.com/data/download_260rtm.htm. Press the Download button to download and install mdac_typ.exe as instructed. Once installed, you should now be able to send attachments from WebMail.
Alternatively, it you may have manually installed WebMail to a virtual directory which is not called ‘webmail’. WebMail must be installed into IIS or PWS into a virtual directory called ‘webmail’.