Hi Yuen,
I understand that you want to point the domain DNS records to your old website in 1and1 after you have verified the domain in Office 365 P1 Plan.
You can point to your website by adding a DNS record in Office 365. For how to do this, please take the steps below:
- Login into MOP(Microsoft Online Portal) as a administrator, click “Admin” in the top.
- Click “Domain” Tab in the left panel, check the checkbox beside the domain that you want to modify
- Click “Manage DNS” in the bottom of your domain list
- In the pop up page, under "DNS manager" Tab, click “New”---“A(Address)”
- Fill in the host name you want (Please note it can’t be the same as your SharePoint Public Website address) and the IP address that your old website located
- Click “Save”, please note it may take up to 72 hours for the records take effect.
Please let me know if you have any concerns about this.