Recently Playing around with Digitalocean's DNS service and found a strange issue that doesn't exists of other DNS provider.
When a record with underscore(s) in it, all subsequent update to that zone won't take effect unless that record is removed.
That means the zone file is updated but external dns query will only get answer from previous records.
I can rule out DNS caching causing the problem, since new record will always get a NXDOMAIN and I tried to query the root DNS server of my domain. I even try to query after TTL but the result is the same as the old zone file.
I am curious what kind of problem is it? And in what situation will this happen?
I've question Digitalocean's support but they seems busy and not interested to this question.
So I post the question here hope someone can point me to the answer.