The defining characteristic of any email forwarding service is that it forwards the email it receives on your behalf to some other mail server. When it comes to spam, this is a problem.
If we forward spam to other mail servers, those other mail servers don't know we didn't originate it. ("Hey, I really got this message from that other guy!" is a common spam sender trick.) If we forward enough of it, they will assume we are spammers and block our forwarders from delivering email to their mail servers entirely. Doing our best to prevent spam is the only way we can assure our continued ability to provide this service.
For that reason, we cannot honor requests to bypass our filtering mechanisms under any circumstances. To do so would threaten not only our ability to forward email to the member requesting it, but also our ability to forward email at all.
This is an unfortunate circumstance, but it's a necessary evil and is true for all viable email forwarding services, not just ours. If you have some special circumstance that requires you to receive spam, spam-like email, or viruses, or if you simply want to exert maximum control over how your email is handled, you will need to eschew the use of any type of forwarding and arrange for a direct-delivery email service that provides that level of control.