When you change a domain's nameservers or DNS records, ISPs (internet service providers) worldwide must update their DNS cache to reflect the change in their areas. The process of updating their DNS cache is called DNS propagation.
In some areas, this process can take from a couple to up to 72 hours, depending on the policies of the ISPs in those areas.
When someone (including you) visits your website, but the DNS propagation is not complete at their ISP or at their end (DNS can also be cached on their browser/computer), they will see the site on your previous hosting, and some emails might arrive at your previous hosting account.
During this time, your websites and emails will be online. If you cannot access them due to DNS propagation, please refer to the following article to access them:
How to view a website without changing nameservers or DNS?
Verify Nameserver:
You can check your domain's nameservers using a third-party DNS tool:https://intodns.com/
