I use postfix on my home server and deliver mail by connecting to my hosting providers' "smart host" using authenticated SMTP.
My home system's hostname is zbmc.eu but I don't use that domain in my E-Mail address, I use isbd.co.uk which domain is hosted at one of my hosting providers (mythic-beasts.com). However most of the time I use my hosting at gandi.net to send my E-Mail, so mail from ch...@isbd.co.uk originates on zbmc.eu, is transferred by authenticated SMTP to mail.gandi.net and is sent on from there to whatever its destination is. As I understand it the SPF records for mail.gandi.net purely confirm to a receiving mail server that the mail is coming from mail.gandi.net and reverse DNS look-up confirms that it really is mail.gandi.net. Have I got that right? I.e. the fact that the mail's From: is not connected in any way to the SPF record is irrelevant. The SPF record simply confirms the SMTP relay host's IP and that it is meant to be relaying mail for that IP. -- Chris Green
