I also sent SMTP+SSL out to my VPS in the US.
I have also use incoming port 80 and 443 ok.
=> BT do not block inbound or outbound SMTP, IMAP(s), HTTP, HTTPS traffic.
Of course you have to sort out your own way of directing SMTP to you dynamic BT IP.
Hope this helps.
BT Faster Total Broadband: 15Mbps