Reading RFC 6844 you will find the definition of “DNS Certification Authority Authorization (CAA) Resource Record”.
You can read everything here: RFC 6844
So, what is CAA anyhow?
In a nutshell you are declaring which your Certificate Authority is for your domain.
It’s another way to verify that the certificate your site is announcing is in fact signed by the issuer that the certificate is showing.
So let’s see what my certificate is showing:
Now, let’s find out what my DNS is telling us:
# dig caa balaskas.gr ;; ANSWER SECTION: balaskas.gr. 5938 IN CAA 1 issue "letsencrypt.org"
You can also use the Qualys ssl server test: