I'm feeling lost in DNS, please help me get back on track.
- I've got a domain. Let's say bar.com And I can add DNS entries for subdomains of type A and CNAME.
- I have another server witch I want to be available as foo.bar.com. And I've got a mail server there.
When I send emails to certain servers from foo.bar.com they get rejected as spam basing on the absence of PTR record. So, the first question is: what can I do to fix it?
Right now I only have an A record at the DNS of registrar of bar.com. I can add all kind of DNS entries for foo.bar.com using name servers of another provider. Right now there no such entries.
And the second question is: can I pull this off without downtime?