Suppose you're connected to a VPN server via an SSTP VPN, and then you're trying to sign in to your webmail account that is already secured with an SSL certificate, e.g. hushmail.com.
However, it seems your original data traffic is double-encrypted by both SSTP & SSL. Now suppose that for any reason your SSTP connection is hijacked and decrypted by a third party, e.g. the attacker stole your SSTP password or your SSTP-signed certificate is a fake one.
My question is: does the ability to decrypt the SSTP traffic pose any threat to the security of your email communication? I mean, does this hijacking of SSTP lead to decrypting the SSL traffic of your email?