We are all faced, from time to time, with the need to change the IP address of our Microsoft Exchange server.
There is no hard relation between the operation of your Exchange server and its IP address thus changing the latter will not break your system.
In short this operation can be considered as safe however it requires a certain level of planning and considerations. I will try to cover in this article the various things you should think about before and after actually changing the IP of your server.
1. Internal DNS
After the IP address is changed make sure that the new IP is registered in the DNS and that the old IP is removed.
Also keep in mind that, if you have a large organization, DNS changes will take sometime to replicate all over and this might temporarily affect your email flow.
2. External DNS
If this IP change will be followed by a change of the public IP of your exchange server you will need to
Change your MX record to reflect the new public IP address
Change any SPF record you have to the new IP address
Create the corresponding PTR record for your new IP and make sure it reflects your mail server FQDN
3. External/Perimeter Network
Depending on the role assumed by the affected exchange server and the configuration of your network you might need to
Change any port forwarding rule to point to the new IP address
If you use a mail filter change the IP this filter relays inbound emails to
If your email server uses a relay host make sure to allow relaying to the new Exchange IP address
4. Internal Network
If you have any application(s) that is configured to use your exchange server to send email based on its IP address these should be also revisited and changed accordingly.
If you are changing to a completely different and new subnet range make sure to update Active Directory Sites to reflect these changes
5. Exchange Server
Finally on the Exchange server itself double check if you have any connector &/or websites bound to a specific IP address instead of all IPs.
In summary, when planned correctly, changing the IP address of an Exchange server is a smooth and risk free operation.