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The Impact of DNS Changes on Email Delivery and Website Accessibility: Unpacking DNS Propagation

If you have reported that a web site is inaccessible, or is displaying the old version, or we have made changes to your email system, we might have directed you to this page. Read this page to understand why this may have happened and what your options are for support.

When a web site is moved to a different server or changes are made to the way email is delivered, an update is usually made to the domains “DNS Record”.

DNS record changes can result in a website appearing to be offline or where one user can see an “old” version of the web site while another can see a “new” version. In the case of email, some inbound emails might get delayed for up to 48 hours. This happens because the change in the DNS record has not spread around all of the systems it needs to.

Your computer, your server if you have one, your router, your internet service providers infrastructure and the primary DNS servers dotted around the globe all need to update themselves with the new DNS record, a process that can take several hours to complete globally.

The process of updating the changed DNS record around the internet is called DNS propagation.

DNS record updates across servers can sometimes be sporadic. A user on one computer or with a certain internet provider might have up to date DNS records but a user on a network with a different setup may not.

To avoid these issues in advance of a DNS change: it is possible to set a “Time To Live” on DNS records. The TTL is like an expiration date for the record. When the TTL expires, servers should request a new copy of the DNS record and update their own information. In our experience, you can’t rely on setting a low TTL. Many ISP’s do not respect this setting, meaning users have to put up with stale DNS records. Setting a lower TTL in advance of any DNS changes often makes no difference at all.

To resolve these issues after a DNS change: if you need to ‘force through” DNS propagation we can provide help to flush the DNS cache on your infrastructure or switch you to a different DNS provider. Generally speaking (unless the problem is mission critical) it might be best to sit tight – full DNS propagation typically takes no more than 24 hours. In situations where other people have problem there is often nothing we can do.

Testing for DNS Propagation:

If you want to check what IP address your own computer has in its DNS record for a web site you are struggling to visit, open up a command prompt or terminal window and “ping” the web site in question. In the example below the ping command shows us  (as far as our own computer is concerned) that our web site is hosted on a server with an IP address of

To check what the global situation looks like you can cross check this against other servers across the world using a tool like Using the same example we can see that the rest of the world also thinks that web site is hosted on a server with the IP address of  In this situation, DNS propagation is complete. The same tool can be used to check “MX records” which dictate where your email is delivered to.