module MailAddressVerifier

# File lib/mail_address_verifier.rb, line 8
def MailAddressVerifier.get_domain(mail_address)
  if mail_address =~ /^[^@]+@(.+)$/
    domain = $1
  else
    raise "Invalid mail address format."
  end
end

# File lib/mail_address_verifier.rb, line 16
def MailAddressVerifier.get_mx(domain)
  Resolv::DNS.new.getresources(domain, Resolv::DNS::Resource::IN::MX)\
    .sort_by {|r| r.preference}\
    .map {|r| r.exchange.to_s}
end

# File lib/mail_address_verifier.rb, line 37
def MailAddressVerifier.verify_by_domain(mail_address)
  result = false
  begin
    mx = get_mx(get_domain(mail_address))
    unless mx.empty?
      result = true
    end
  rescue
    result = false
  end
  result
end

# File lib/mail_address_verifier.rb, line 22
def MailAddressVerifier.verify_by_smtp(mail_address, myhost, myaddress)
  mx = get_mx(get_domain(mail_address)).first
  result = false
  Net::SMTP.start(mx) do |smtp|
    smtp.helo myhost
    smtp.mailfrom myaddress
    begin
      smtp.rcptto mail_address
      result = true
    rescue
    end
  end
  result
end