Michael R. Brumm wrote:
But ideally you wouldn't use an IP address because they might change that (move the
server to a different subnet due to security or management reasons). If you are relaying
through a host name like "smtp.ntl.com", then this would be best:
"v=spfv1 a:smtp.ntl.com -all"
*Ideally* they would actually provide their own SPF record for you to refer to:
"v=spfv1 redirect=customer.ntl.com"
They would then maintain the SPF TXT record for customer.ntl.com with an up to
date list of the IP addresses of their outgoing mail servers, which may not be
the same as the IP addresses that they accept submissions from customers on
(i.e. the addresses corresponding to the name smtp.ntl.com or whatever).
Paul.