Migration: MailFlow and DNS PTR Record Readiness
Recently I have been working on a Migration deployment and Lets have a look on the import points to check during mail routing gateway change.
While migrating outbound gateway Exchange server from 2003 to 2010 on the Exchange side, we just need to ensure port 25 is open from SMTP gateway and DNS is resolving MX records for destination.
But Is this enough? Let us see later.
Now in my customer environment during the cutover, we just created a send connector in Exchange 2010 and remove the smtp connector in 2003. Mail start flow, test with gmail and yahoo. After some time I found some domains emails were stuck in the queue which were blocked by recipient.
The issue was identified as no reverse lookup record available.
We informed the network group to get the PTR record created to move the mail routing back to Exchange 2003.
Network group checked with domain registrar but registrar suggested to go to ISP who has given the IPs.
Meanwhile I created their SPF record which was missing as well with PTR entry in it. Moved the mail routing to Exchange 2010 but again I was out luck got the below message
Option 1: Now we were left with 2 options, either move the IPs from Exchange 2003 to Exchange 2010
Option 2: Create new PTR record.
While we plan for a mail routing migration, verify if we have PTR records available. If they are not available then get them created or plan moving the IPs to new mail routing Gateway.
Also keep in mind creating SPF record will help in keeping IP out of blacklisting but will not protect from reverse lookup check.
Microsoft Solution Architect | Exchange Server