@rhmk Is not available this week, so I removed him from the list of reviewers.
@rob0d Please have a look at this PR and comment.

@berndfinger yes, it would make it safer and more flexible to make the strict check optional and use something like sap_general_preconfigure_dns_check_strict: false as a default.
We can possibly also enhance the PTR check to search through all returned records in a hope that one will match as mentioned in #784 as it will possibly help with the Azure behaviour that @sean-freeman mentioned. I'm not sure if it's worth the effort though.
I can have a look at this, but I am away until 15th July.

I'm going to merge this PR now to get back the previous default behavior while also implementing an option to enforce strict DNS checking. We can continue discussing further options in the issue and see if we want or can improve the DNS checking later.