I've got a droplet running a site (let's call it example.com). For a variety of historical reasons, the site's domain is registered at Dreamhost, which is currently providing the domain's DNS and mail service. This is working fine EXCEPT that the site (based on Drupal 7) is not able to send mail to an address at example.com -- when I track /var/log/maillog, Postfix reports that the attempt to send fails because of an unknown user (yes, the user really exists in the Dreamhost mail system); this happens both when Drupal (php, really) tries to send mail and when I manually send mail from the shell via mailx. Outgoing mail from the site is in fact working, by the way; I can send to addresses other than example.com via both php and mailx. Finally, I'm not running a DNS server as part of the droplet.
(1) How do I get the site to understand where its mail server is? I'd like to leave the mail service at Dreamhost for now, but I'm open to moving the DNS service to DigitalOcean if that makes things easy/possible.
(2) Once mail is working, I'll want to set up SPF records for the domain. I guess it'll be obvious where/how to do that, but that will be an issue down the road.
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