SRV RECORDS

You can refer the following link to create SRV records for the domains :

https://support.office.com/en-au/article/Create-DNS-records-for-Office-365-at-any-DNS-hosting-provider-7b7b075d-79f9-4e37-8a9e-fb60c1d95166?ui=en-US&rs=en-AU&ad=AU