Propagation – If you change your email or website services you will need to change records on your domain to point the traffic to the new service provider’s server.
When changing the domain’s records a delay will occur which we call Propagation.
Internet Propagation is the process by which computers across the Internet update their information from one another.
Propagation works like this:
You purchase a domain name or change your domain name servers (records). That information is changed on your registrar’s DNS server.
Other servers periodically connect with your domain registrar’s server for updates. These servers will then update their own records to match your registrars. If these other servers are major Internet services, then other servers may in turn update from them. In this way, the new information will spread across the Internet. This is called Propagation.
Unfortunately not all servers update at the same time, or the same number of times per day. Large Internet service providers may even have more than one server and those may not update at the same time either. Because of this, up to 48 hours after you change or set up a domain name it may seem to work intermittently, or to work from some areas and not others. This is normal. After 48 hours your website will be live for everyone.
Propagation status tool
www.whatsmydns.net lets you instantly perform a DNS lookup to check a domain names current IP address and DNS record information against multiple name servers located in different parts of the world.
This allows you to check the current state of propagation after having made changes to your domains records so at least you know when propagation has completed.