Webmail Helper Hacked? (base64 encode tampering)

Hi all,

I have been using the webmail helper recently but have noticed a number of "spoofed" IP's posting (testing holes?). The strange thing is I am using the anti forgery token as well as html encoding the user input but the post arrive as base64 encoded. When I submit via the site the post always come through as asci, heres the two headers from the email:

Content-Type: text/html; charset=us-ascii
Content-Transfer-Encoding: quoted-printable

versus the tampered (???)

Content-Type: text/html; charset=utf-8
Content-Transfer-Encoding: base64

Can anyone help me with diagnosing if this is a breach of one of the back end systems or a possible vulnerability in the webmail helper?

Cheers,

Jus