README.md in valid_email2-5.1.1 vs README.md in valid_email2-5.2.0

@@ -49,13 +49,19 @@
 
 To validate strictly that the domain has an MX record:
 ```ruby
 validates :email, 'valid_email_2/email': { strict_mx: true }
 ```
-`strict_mx` and `mx` both default to a 5 second timeout for DNS lookups.  To
-override this timeout, specify a `dns_timeout` option:
+`strict_mx` and `mx` both default to a 5 second timeout for DNS lookups.  
+To override this timeout, specify a `dns_timeout` option:
 ```ruby
 validates :email, 'valid_email_2/email': { strict_mx: true, dns_timeout: 10 }
+```
+
+Any checks that require DNS resolution will use the default `Resolv::DNS` nameservers for DNS lookups.  
+To override these, specify a `dns_nameserver` option:
+```ruby
+validates :email, 'valid_email_2/email': { mx: true, dns_nameserver: ['8.8.8.8', '8.8.4.4'] }
 ```
 
 To validate that the domain is not a disposable email (checks domain and MX server):
 ```ruby
 validates :email, 'valid_email_2/email': { disposable: true }