Dns records updating
Some ISPs ignore TTL settings and only update their cached records every two to three days.Although we ensure 1 hour for A/AAAA/MX/TXT/CNAME-records and 48 hours for NS-records, it might take up to 72 hours until the settings are visible.When Office 365 finds the correct TXT record, your domain is verified.
If Crazy Domains is your DNS hosting provider, follow the steps in this article to verify your domain and set up DNS records for email, Skype for Business Online, and so on. To learn about webhosting and DNS for websites with Office 365, see Use a public website with Office 365.
The name server does not have to return these records if it chooses not to do so (for example, to reduce the size of the response).