I have just started introducing Zend Framework when I had to face the problem with output multiple error messages in form while email address validation. Checking domain (whith is enabled by default) causes additional error messages indicates anomalies in hostname segment of provided by user email address. In result, we receive several errors assigned to one email field.

The problem is easy to slove by overriding default behaviour of Zend_Validate_EmailAddress clearing all messages generating while validation and setup a new single error message.

Simply add namespace MyOwn_ for own needs and provide class in file /libraries/MyOwn/Validate/EmailAddess.php

class MyOwn_Validate_EmailAddress extends Zend_Validate_EmailAddress
{
  const INVALID = 'emailAddressInvalid';

  protected $_messageTemplates = array(
    self::INVALID => "Invalid Email Address."
  );

  public function isValid($value)
  {
    parent::setOptions(array(
      'allow' => Zend_Validate_Hostname::ALLOW_DNS,
      'domain' => true,
      'mx' => true,
      'deep' => true)
    );

    if(!parent::isValid($value)) {
      $this->_messages = array(); // clear all previous messages
      $this->_error(self::INVALID);
      return false;
    }

    return true;
  }
}

And provide above custom validator to form element in /application/forms/AccountRegister.php:

class Form_AccountRegister extends Zend_Form
{
  public function init()
  {
    $this->setMethod('post')
         ->setName('Account_Register');
    
    $email = new Zend_Form_Element_Text('email');
    $email
      ->setLabel('Email address')
      ->addValidator(new ZendUtil_Validate_EmailAddress)
      ->setRequired(true);
    
    $this->addElement($email);
    
  }
}

NOTE:

• In addition, you can simply translate the emailAddressInvalid message.
• For sticklers, setting options in isValid method is hardcoded with look like a messy code, but it is quick-fix

Hope it will help.