As mentioned here, mail server Reverse-DNS (PTR record) must configured well. most offen the FQDN is not in own control and it is defined by the ISP provider. and it never equals with mail server domain name. Requesting the ISP to change it, is not available, they don't change it. so:
Thanks.
Because of what you are trying to do I would suggest that you try hosting your email with a hosting provider and get your own domain so you can make any of those changes as require. Now as for your questions:
Does using this fqdn is use-less in mail server setup?
You Should use fqdn.
How to verify that it is configured correctly?
As stated by wtayyeb you can use dig ie:
# get A record for domain
$ dig +short mail-vn0-f47.google.com
209.85.216.47 <--------------------- A record
# get reverse record for the A record & verify reverse matches domain
$ dig +short -x 209.85.216.47
mail-vn0-f47.google.com. <---------------- IP resolves back to domain
As you can see IP resolved back to the originating FQDN.
Is there any webtools to check it?
Yes theres a few webtools out there. One that I've used in the past & its pretty good is:
If you need more webtools its always easy enough to google for test PTR or rDNS records.
Hopefully that's what you were looking for & keep in mind that hosting your domain with a hosting service { like dreamhost.com :) } will probably be the best way to set all your email stuff up.
Not really sure what you are asking for in #1. Are you asking if a PTR record is used in a mail server setup? Technically no it is not, but as a PTR record is used as the counterpoint for an A record, there are merits to having it properly configured (also, depending on other servers configurations regarding doing lookups to authenticate your server, it can affect mail flow if not properly configured).
Let's take a step back.
Mail is routed to you based on MX records that point your domain to the appropriate FQDN. This FQDN then has an A record configured for it so that you can translate its name to an IP address. A PTR record allows you to do a lookup based on the IP address to make sure that what is returned is the FQDN that in turn has an A record pointing to the same IP. This is why it is also referred to as a circle check as one gets you to the other one and vice versa.
Now keep in mind that mail flow in to your domain does not equal mail flow out of your domain. Small organization may have the same ingress/egress path, but many organizations do not, so looking at an MX record will show you where inbound email is sent, this is not necessarily where outbound email comes from.
I am sure there are automated tools to check for records, but I would recommend becoming familiar with either nslookup (Windows) or dig (Linux), or both, to do your lookups manually. This will let you query against the DNS servers your system normally does, as well as allowing you to manually do lookups against other DNS servers (so you can verify results both internally and externally).
Are you looking to resolve a specific issue, verify a specific configuration, or just educating yourself on how the various DNS records are used?
