Quote:
Originally Posted by n5bb
Your DNS records include a TTL (Time To Live) field for each record. The TTL value specifies the requested time (in seconds) that DNS entries (such as MX) are cached. See:
https://en.wikipedia.org/wiki/Time_to_live
So if your old TTL value for the email related records (MX, SPF TXT, DMARC TXT) was 86,400 (one day), then over one day (maybe two days) before the changeover date you would change those TTL values to something small (such as 600 for 10 minutes). Then after the original TTL delay has passed (with some additional delay for good measure), you can change the DNS records (and their TTL values) to the new values.
Some servers may check your DNS records sooner than the TTL value specifies. But you can't depend on them using the new DNS record values until after the TTL-specified delay expires. This also depends on when the servers happened to have a need to check your DNS records. This is why some email servers may use the old MX value and others the new value.
Your sites should be: - Examine your old TTL values and write them down.
- Change the TTL values of DNS records you will be changing to a small value (maybe 600). Be sure you verify that the authoritative DNS TTL values are actually changed by running a test.
- Wait a bit longer than the original (old) TTL delay time. After that delay, any check of your DNS records should indicate a small TTL, so your MX entry should not then be cached very long by servers following the rules.
- Change your DNS MX and other email-related records to the new desired values, including new TTL values (maybe an hour or a day).
But note this warning at the Wikipedia entry:
Also, some services accept different characters in the email address. Don't use any non-standard characters in your email address.
Bill |
Yeah about 2 weeks before I changed to Fastmail I set the TTL in Cloudflare (which manges my DNS) to 1 min for my MX records. You're right though that some DNS caches.. However, I'm pretty sure between Nov 20 to Dec 1 the cache would have expired (at least I hope so??) So while the cache can explain why email may not flow immediately after the change, it doesn't (or shouldn't) explain why it doesn't flow after a few weeks.