### A.1.2. CAA contactphone Property
SYNTAX: `contactphone `
The CAA contactphone property takes a phone number as its parameter. The entire parameter value MUST be a valid Global Number as defined in RFC 3966, Section 5.1.4, or it cannot be used. Global Numbers MUST have a preceding + and a country code and MAY contain visual separators.
The following is an example where the holder of the domain specified the contact property using a phone number.
```DNS Zone
$ORIGIN example.com.
CAA 0 contactphone "+1 (555) 123-4567"
```
The contactphone property MAY be critical if the domain owner does not want CAs who do not understand it to issue certificates for the domain.