DNS changes not visible yet: propagation and TTL

What it means

When a server needs your SPF, DKIM or MX record, it does not ask your DNS provider every time. It asks once and keeps the answer in a cache for a while. That duration is the TTL (time to live), set on each record in seconds.

• 300 = 5 minutes
• 3600 = 1 hour
• 86400 = 24 hours

Until the cache expires, some servers still see the old value. This delay is called "propagation".

Why it matters

After a fix, your test may still fail for a while, and you may think the fix did not work. Worse, you may change things again and create a real mistake. Knowing how caching works helps you wait the right amount of time.

How long to wait

• A new record (that never existed): usually a few minutes. But if someone looked it up just before you created it, the "does not exist" answer is also cached, sometimes for up to an hour or more.
• A changed record: up to the old TTL. If the old TTL was 24 hours, some servers may see the old value for a day.
• New nameservers (moving your whole DNS to another host): up to 24 to 48 hours.
• Some DNS providers also take time to publish your change after you click "Save".

How to check the real value

1. Ask your DNS host directly. Find your nameservers (for example ns1.your-dns-host.com), then ask them, which skips all caches:

   dig TXT yourdomain.com @ns1.your-dns-host.com
   dig TXT _dmarc.yourdomain.com @ns1.your-dns-host.com

2. If that answer is wrong, the problem is not propagation: the record was not saved, is at the wrong name, or you edited DNS at a provider that is not in use. Check which nameservers your domain really uses.
3. If that answer is right, just wait. Public tools like the Google Admin Toolbox Dig show what large resolvers see.
4. Use the Domain scanner at /domain-scanner to see your SPF, DKIM, DMARC and MX records as a receiving server would.

Plan big changes ahead

• A day before changing an important record (MX, SPF), lower its TTL to 300. Wait for the old TTL to pass, make the change, then raise the TTL again (3600 is a good normal value).
• When changing email provider, keep the old mailboxes working for two days, because some emails may still arrive there.
• Do not change the same record many times in a row. Make one careful change and wait.

Check that it is fixed

Once your DNS host gives the right answer and the TTL has passed, run the Domain scanner again. Then send a new test email from the Delivmail home page: the report reads the records fresh at the time of the test and should show them passing.