I'm a little confused about the setup of a PTR record for reverse dns lookup.
We are hosted at Rackspace and we have a front end webserver and behind that an appserver. Users don't access the Appserver directly, they go through the webserver.
Webserver: www.domain.com 190.1.2.3
Appserver: app.domain.com 170.2.3.4
The appserver sends out all the email with from address suck as [email protected]
So, how do I set up the PTR / reverse dns configuration? I was thinking that it should be as follows:
Reverse dns record on Appserver:
170.2.3.4 = app.domain.com
DNS
A *.domain.com 190.1.2.3
A app.domain.com 170.2.3.4
TXT app.domain.com "v=spf1 ip4:170.2.3.4 ~all"
TXT domain.com "v=spf1 ip4:170.2.3.4 ~all"
Would this be the correct way to set that up?
~all
; it's completely pointless, and may be actively harmful. See my answer to our canonical question on the subject for more details on why you should only publish records that end in-all
.-all
is the way to go for all SPF records. It's just that the more complex your mail setup is, the more trouble you will have to take to list all the valid senders for your domain. In some cases seen on SF, it's not possible within the DNS lookup limits of the protocol; for such people (who've usually allowed large numbers of third-party-hosted services to send email badged from them), SPF is unsuitable, and they simply can't use it.