Portal Home > Knowledgebase > Google Message Security > Delay when making DNS MX Record changes
Issue
Why is there a delay when making DNS MX record changes?
Resolution
DNS record changes MX (and any other DNS) record latency is controlled by a TTL (Time to Live) field on each record. This field is configured in the Authority DNS server for the domain by the domain's technical contact.
Here is how it works:
1) The first time a DNS server is polled for new information, it requests that information from the Authority for the domain.
2) At that point, the information and TTL is downloaded and applied.
3) Further requests within the TTL time period are resolved based on cached information.
4) When the TTL expires, the Authority server is polled for new information.
This means that it will take a full TTL time period to propagate new DNS entries across the Internet. When routing traffic to Postini suggests you change your DNS MX TTL to 600 seconds. It will take the full previous TTL for your new TTL to change. However, after the change, it will only take 10 minutes for you to propagate your new MX entries.
Additional Information
The reason for this caching is to provide configurable DNS caching, thereby preventing all DNS servers on the Internet from being constantly overloaded with requests.
The best tool for examining these records is the "dig" utility.
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