Suppose foo.org lives on a single droplet. It’s using digitalocean’s DNS servers
Do I need an A record for mail.foo.org? Is this true for all DNS, or specific to digital ocean?
Is the same thing true for other pseudo-hosts (www.foo.org)?
But AFAICT, my previous DNS provider did not have an A record for mail.foo.org(*). And when I switched back to my old DNS provider, mail was once again received on the droplet
Much the same story with www.foo.org, except that it looked as if http://www.foo.org was successfully pointing to the nginx server on the droplet. (But maybe I was confused by DNS propagation delays.)
FWIW, the hostname I gave to the droplet is neither mail nor www.
And all the config files for postfix and nginx know about all the hosts they are supposed to be pretending to be - the only variable is DNS.
I’ve been making liberal use of commands like “dig @ns1.digitalocean.com mail.foo.org all” to try to compare what the two are saying, but what I see doesn’t make sense given the pattern of bouncing mail etc.
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