DNS Changes Required for Exchange Online

The following are examples of DNS records required for Office 365 Exchange Online. With an on premise environment that might not have been fully decommissioned yet, I recommend not only creating these records publicly but also in your private DNS servers.

MX

The MX record is required for routing mail to the appropriate destination. Without it, mail will not be received.

  • Priority: 0
  • Host Name: @
  • Target: <domainname-com>.mail.protection.outlook.com; Example: wordpress-com.mail.protection.outlook.com

 

CNAME (Autodiscover)

The Autodiscover CNAME record for is essential for mobile device and Outlook client connectivity. It is also important to note that this is a CNAME record; not an A record. I have seen too many times this created as an A record but it will not work as Microsoft expects a CNAME record for autodiscover.

  • Priority: N/A
  • Host Name: autodiscover
  • Target: autodiscover.outlook.com

 

SRV (Autodiscover)

Though a valuable record for an on premise environment (i.e. _autodiscover._tcp.domainname.com), it appears that it is not a required DNS record for Office 365.

 

TXT (SPF)

The value for an SPF record is the same for all accounts with Office 365…

  • Host Name: @
  • Value: v=spf1 include:spf.protection.outlook.com -all

…however, if an on premise environment still exists, the external IP address of that Exchange environment will need to be added to the SPF record to ensure delivery of all messages without NDRs. For example, simply add “ip4:” and the external IP address to the record Office 365 requires.

  • Host Name: @
  • Value: v=spf1 include:spf.protection.outlook.com ip4:108.108.200.200 -all

 

Reference(s):

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