I run my own home-lan email server and have inbound SMTP and IMAPS.
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.

Thanks guys for the info and for pointing me in the direction of that page. I've ordered it, so time will tell, and i'll just have to work around any issues.