DNS validation succeeds for missing mx records

[tpetry]

The email address xxx@icluod.com (transposed o and u) passes dns validations, but in my opinion it should not. The dns validation recognizes that the icluod.com domain has an A record but no MX record. The validation is successful and a warning is stored that no mx record could be found.

But is this really the correct semantics that the dns validator should do? For this domain, it will return that everything is valid and you can send an email to the recipient. However, if you check the warnings (which not everyone will do), you will see that it is indeed invalid, since there is no mx record for the domain.

One could argue that the caller has to add the logic for checking the warning. The laravel framework (#34092) believes that the return code is the only relevant result for detecting whether an email address is correct and warnings should not lead to a validation error. That is, it would only fail if this library changes its behavior.

So what is the reason for the current (strange?) behavior.

[egulias]

Hi @tpetry , it is a valid point the one you are rising. The DNS validation was inherited in "logic" from Dominic Sayer's "isemail" function/lib.
In that, the non-existance of an MX records has this same behaviour.

The point is that changing a behaviour would force a major version change. I'm working on a new version and it could fit.

Meanwhile I can suggest you add the logic by wrapping the validator in a new validator implementing the interface. I think very recently this ability was merged into laravel.

[ThibaudDauce]

Hi,

The RFC says that if a MX is not present, the domain is still valid with a A or a AAAA record. The new implementation could refuse valid email addresses.

https://en.wikipedia.org/wiki/MX_record

In the absence of an MX record, email senders will attempt delivery to the address record - e.g. example.com.

This is based on RFC 5321 sec. 5, which states :

SMTP clients must look up an MX record;
If (and only if) no MX record for the domain is present, treat the domain as if it had an MX record with the given domain as the target hostname and a preference value of 0
Perform A or AAAA lookups as required to determine the IP address of the target hostname

[egulias]

Behaviour change has been done for v3 to be a little bit more "real life" friendly.