set a DNS timeout

README.md

@@ -47,10 +47,15 @@ To validate that the domain has an MX record or A record:
 ```ruby
 validates :email, 'valid_email_2/email': { mx: true }
 ```
+
 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:
+```ruby
+validates :email, 'valid_email_2/email': { strict_mx: true, dns_timeout: 10 }
 
 To validate that the domain is not a disposable email (checks domain and MX server):
 ```ruby

lib/valid_email2/address.rb

@@ -20,9 +20,10 @@ def self.prohibited_domain_characters_regex=(val)
       @prohibited_domain_characters_regex = val
     end
 
-    def initialize(address)
+    def initialize(address, dns_timeout = 5)
       @parse_error = false
       @raw_address = address
+      @dns_timeout = dns_timeout
 
       begin
         @address = Mail::Address.new(address)
@@ -132,12 +133,14 @@ def address_contain_emoticons?(email)
 
     def mx_servers
       @mx_servers ||= Resolv::DNS.open do |dns|
+        dns.timeouts = @dns_timeout
         dns.getresources(address.domain, Resolv::DNS::Resource::IN::MX)
       end
     end
 
     def mx_or_a_servers
       @mx_or_a_servers ||= Resolv::DNS.open do |dns|
+        dns.timeouts = @dns_timeout
         (mx_servers.any? && mx_servers) ||
           dns.getresources(address.domain, Resolv::DNS::Resource::IN::A)
       end

lib/valid_email2/email_validator.rb

@@ -5,14 +5,14 @@
 module ValidEmail2
   class EmailValidator < ActiveModel::EachValidator
     def default_options
-      { regex: true, disposable: false, mx: false, strict_mx: false, disallow_subaddressing: false, multiple: false }
+      { regex: true, disposable: false, mx: false, strict_mx: false, disallow_subaddressing: false, multiple: false, dns_timeout: 5 }
     end
 
     def validate_each(record, attribute, value)
       return unless value.present?
       options = default_options.merge(self.options)
 
-      addresses = sanitized_values(value).map { |v| ValidEmail2::Address.new(v) }
+      addresses = sanitized_values(value).map { |v| ValidEmail2::Address.new(v, options[:dns_timeout]) }
 
       error(record, attribute) && return unless addresses.all?(&:valid?)