Here is a quick intro to SPF and how to configure it:
SPF (Sender Policy Framework) is a countermeassure for beeing an unwilling wictim of spam sending. Using SPF you can approve from what SMTP servers email from @yourdomain.com will be sent from. This will make it harder to spoof your e-mail adrress, as long as the receipient server checks the SPF record.
For Office365 you need to update your DNS zone with SPF records to fully validate the domain. Here is an example of how the SPF record shuld look like:
v=spf1 include:spf.protection.outlook.com -all
If you are using some system to send out e-mails outside Office365 you need to add those servers to you SPF record.
If you just want to add a IP adresse this is how your record shuld look like:
v=spf1 include:spf.protection.outlook.com ip4:188.8.131.52 -all
And if you want to use a hostname (and a IP address) it could be like this:
v=spf1 include:spf.protection.outlook.com ip4:184.108.40.206 a:mail.sender.com -all
Note that using include will require the domain (ie_ spf.protection.outlook.com) to have its own SPF record to be valid.