BT Customers Outgoing Mail
All customers of BT retail or BT business who currently use our SMTP services are advised to change their outgoing email server to BT’s own system.
BT themselves add a positive RBL (blacklist) spam score (i.e. more spam) to all BT customers who do not use their own BT outgoing mail servers despite authentication and SSL.
Please reference: http://www.spamhaus.org/pbl/query/PBL231592
We find this situation quite disturbing considering BT only offer plain SMTP authentication and not SSL as we do, nor do they offer domainkey or SPF validation for your domain.