DNS records and Exchange, it’s not really hard but it’s very important to configure them correctly. Incorrect DNS records and especially pointer records can cause issues with mail delivery.
Which records are needed to send and receive mail with Exchange:
A-record, this record ensures that a namecan be translated to an ip-address, for example mail.domain.com
PTR-record, this record is used for reverse lookup. By performing a query for the IP-address and then check if this leads to the FQDN of the mailserver a cross check is done if the mailserver is really who he claims to be.
MX-record, you can have multiple records of this type. Each entry is a mailserver where mail can be delivered to. Each rule has a priority, depending on the priority the message will be delivered to a mailserver. For example: if you have 2 records one with a priority of 10 and another with a priority of 99. The sending mailserver will first try to deliver the mail to the server with the priority of 10 if that one doesn’t react it will deliver the mail to the mailserver with priority 99.
SPF-record, this type of record is optional. This record contains all FQDN’s/ip-addresses of servers who may send mail with your domain as sending domain. This can be used by the receiving mailserver to check if the mailserver who sends the e-mail if allowed to send mail from that specific domain.
Besides the DNS-records for sending and receiving DNS records are also used for autodiscover:
A-record, this record ensures just like the A-record for sending and receiving that the name will be translated to an ip-address, in the case of autodiscover this needs to be the following syntax: autodiscover.domain.com
SRV-record, this record can beused instead of the A-record to let Outlook 2007 users use the autodiscover service. This record contains external FQDN of the CAS-serve which the user usages to connect to Exchange. If you want to use this type of record ensure that any other A or CNAME record used for autodfiscover is removed.
For this kind of stuff there are enough tools, below a short overview of tools I use often:
EmailTalk, site with several tools: ptr, mx or spf record check open
MXtoolbox, site with several tools: mx record check, RBL check and test your mailserver from outside open
Microsoft SPF Record Wizard, site which helps to create a SPF record open
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