Raw emails needed for testing

Question

I'm playing around with a new C# email library and would like to test it as much as possible. I've used several POP3 email servers (e.g. Exchange, Hotmail, Gmail, etc.) to test support for the most popular email MIME formats e.g. text/plain, multipart/alternative, etc.

Does anyone know if there is a repository of sample emails that I can use to further test more obscure MIME formats e.g. application/pkcs7 etc.

This is to make sure the library is robust enough to handle these types of emails. Thanks.