ENGCOM-6568: magento/magento2#: Remove unused “Default Email Domain” option and related to it code #26000

Author: lenaorobei

app/code/Magento/Customer/etc/adminhtml/system.xml

@@ -86,9 +86,6 @@
                     <comment>To show VAT number on Storefront, set Show VAT Number on Storefront option to Yes.</comment>
                     <source_model>Magento\Config\Model\Config\Source\Yesno</source_model>
                 </field>
-                <field id="email_domain" translate="label" type="text" sortOrder="60" showInDefault="1" showInWebsite="1" showInStore="1" canRestore="1">
-                    <label>Default Email Domain</label>
-                </field>
                 <field id="email_template" translate="label comment" type="select" sortOrder="70" showInDefault="1" showInWebsite="1" showInStore="1" canRestore="1">
                     <label>Default Welcome Email</label>
                     <comment>Email template chosen based on theme fallback when "Default" option is selected.</comment>

app/code/Magento/Customer/etc/config.xml

@@ -16,7 +16,6 @@
                 <confirm>0</confirm>
                 <default_group>1</default_group>
                 <tax_calculation_address_type>billing</tax_calculation_address_type>
-                <email_domain>example.com</email_domain>
                 <email_identity>general</email_identity>
                 <email_template>customer_create_account_email_template</email_template>
                 <email_no_password_template>customer_create_account_email_no_password_template</email_no_password_template>

app/code/Magento/Customer/i18n/en_US.csv

@@ -432,7 +432,6 @@ Strong,Strong
 "Default Value for Disable Automatic Group Changes Based on VAT ID","Default Value for Disable Automatic Group Changes Based on VAT ID"
 "Show VAT Number on Storefront","Show VAT Number on Storefront"
 "To show VAT number on Storefront, set Show VAT Number on Storefront option to Yes.","To show VAT number on Storefront, set Show VAT Number on Storefront option to Yes."
-"Default Email Domain","Default Email Domain"
 "Default Welcome Email","Default Welcome Email"
 "Email template chosen based on theme fallback when ""Default"" option is selected.","Email template chosen based on theme fallback when ""Default"" option is selected."
 "Default Welcome Email Without Password","Default Welcome Email Without Password"

app/code/Magento/Sales/Model/AdminOrder/Create.php

@@ -28,11 +28,6 @@
  */
 class Create extends \Magento\Framework\DataObject implements \Magento\Checkout\Model\Cart\CartInterface
 {
-    /**
-     * Xml default email domain path
-     */
-    const XML_PATH_DEFAULT_EMAIL_DOMAIN = 'customer/create_account/email_domain';
-
     /**
      * Quote session object
      *

app/code/Magento/Sales/etc/di.xml

@@ -1000,9 +1000,6 @@
                 <item name="sales_email/shipment/copy_to" xsi:type="string">1</item>
                 <item name="sales_email/shipment_comment/copy_to" xsi:type="string">1</item>
             </argument>
-            <argument name="environment" xsi:type="array">
-                <item name="customer/create_account/email_domain" xsi:type="string">1</item>
-            </argument>
         </arguments>
     </type>
     <preference