Hi Eoin,
I checked the custom domain information with NsLookup Tools, and found that the Name Server records pointed to Office 365.
In terms of the situation, if you want to keep the website with current hosting provider, you need to add an A record on Office 365 portal manually, follow these steps:
1. On the Admin page, under Management, click Domains, and select the domain that you’d like to edit.
2. Click Manage DNS, click New, and then choose A (Address).
3. On the Add a DNS record page, type the following:
For Host name or Alias, type @
For IP Address, type the IP address where your website is currently hosted, for example: 172.16.140.1
4. Click Save.
5. You can also create a CNAME record to help customers find your website. On the DNS manager tab, click New, and then choose CNAME (Alias).
6. On the Add a DNS record page, type the following:
For Host name or Alias, type www
For Points to address, type the fully qualified domain name (FQDN) for your website. For example: contoso.com
7. Click Save.
Tips: 1.You don’t need to change the A record.
2. Don’t change the website address to custom domain on Office 365 portal.
Thanks,
Ida Qiu
