How to spell spf correctly?

Question

SPF

Programmers tell me that many allowed ip values ​​are not correct in spf records.
------------
You need this:
A domain / 16 subdomains = 16 ip
Permission must be registered so that 16 subdomains - domain A can send mail for domain B
, since domain B already has spf records, add 16 more - not right? Maybe not 16 but more for example.
Permission by range - not the fact that the hoster will give 1 block of ip address and I think it's not correct to allow the block either. I think the design is somehow trickier here - I know they do it, as I ask for your advice.

Answer 1

Yes, there is a 10 request limit when SPF is enabled.
Letters are sent not by subdomains, but by mail servers, and they are specified in the SPF policy. If you have 16 mail servers, you can register their IP addresses. There are no restrictions on IP addresses in the policy.

Answer 2

Evgeny Matveev , to check the correctness of the SPF record syntax (including also the limit of 10 DNS queries), before publishing it in the DNS zone, you can use the following tool:
https://easydmarc.com/tools/spf-record-raw-check- v...