Checks the TTL (Time to Live) for the SPF record.
SPF records only need to be changed when the website changes how it sends email. This should be infrequent and planned ahead of time. Therefore, a short TTL for an SPF record is unnecessary and can cause extra DNS traffic. We recommend a TTL of 1 day, but this test will only produce a warning if the TTL is shorter than 1 hour or longer than 1 week.