DNS
What is TTL (Time To Live)?
The number of seconds DNS resolvers are allowed to cache a record before re-querying it.
TTL is a value attached to each DNS record that tells resolvers how long to cache the answer before fetching a fresh copy. Low TTLs such as 300 seconds make changes take effect quickly but increase query load, while high TTLs reduce lookups but slow updates. Caches honor the TTL that was in effect when they last fetched the record, so lowering a TTL only speeds up changes made after the old value expires.
Why it matters for cold email
When rotating sending domains, updating SPF or DKIM, or repointing MX during cold-email setup, a high TTL means receivers keep serving stale authentication records for hours, causing intermittent auth failures. Lowering TTL ahead of planned changes makes fixes take effect fast and predictably.
Related terms
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