“DNS propagation” is one of the most misunderstood parts of managing a website or business email. Here is what is actually happening when you make a DNS change.
DNS records are cached, not instantly synced
When you update a DNS record, that change is made at your DNS provider. However, other servers around the internet — including your internet provider’s resolver and countless intermediate caches — may have already cached the old value, based on the record’s TTL (time to live) setting.
TTL determines how long old data can linger
Every DNS record has a TTL, telling other servers how long they are allowed to cache it before checking again. A record with a one-hour TTL should update everywhere within roughly an hour after the cache expires. A record with a 24-hour TTL can take much longer to be seen everywhere.
Planning around propagation
Before a planned migration or cutover, it is common practice to lower the TTL on the relevant records in advance, wait for the old TTL to expire, make the change, and only then restore a normal TTL. This reduces the practical delay significantly.
Why some people still see the old site or mailbox
If you or a colleague still see the old website or mail server after a change, it is often a local or ISP-level cache rather than a sign the change failed. This usually resolves on its own within the cached TTL window.
We plan DNS changes and cutovers as part of every domain and DNS project, including migrations and hosting moves, to keep this disruption to a minimum.