Addressed review comments

Author: Graham Wharton

app/code/Magento/Sales/Model/Order/Email/SenderBuilder.php

@@ -6,6 +6,7 @@
 namespace Magento\Sales\Model\Order\Email;
 
 use Magento\Framework\Mail\Template\TransportBuilder;
+use Magento\Framework\Mail\Template\TransportBuilderByStore;
 use Magento\Sales\Model\Order\Email\Container\IdentityInterface;
 use Magento\Sales\Model\Order\Email\Container\Template;
 
@@ -30,11 +31,13 @@ class SenderBuilder
      * @param Template $templateContainer
      * @param IdentityInterface $identityContainer
      * @param TransportBuilder $transportBuilder
+     * @param TransportBuilderByStore $transportBuilderByStore
      */
     public function __construct(
         Template $templateContainer,
         IdentityInterface $identityContainer,
-        TransportBuilder $transportBuilder
+        TransportBuilder $transportBuilder,
+        TransportBuilderByStore $transportBuilderByStore = null
     ) {
         $this->templateContainer = $templateContainer;
         $this->identityContainer = $identityContainer;

lib/internal/Magento/Framework/Mail/Template/TransportBuilder.php

@@ -173,16 +173,17 @@ public function setReplyTo($email, $name = null)
     /**
      * Set mail from address
      * 
-     * @deprecated Use setFromByStore
+     * @deprecated This function sets the from address for the first store only.
+     * new function setFromByStore introduced to allow setting of from address
+     * based on store.
+     * @see setFromByStore()
      *
      * @param string|array $from
      * @return $this
      */
     public function setFrom($from)
     {
-        $result = $this->_senderResolver->resolve($from);
-        $this->message->setFrom($result['email'], $result['name']);
-        return $this;
+        return($this->setFromByStore($from));
     }
 
     /**

lib/internal/Magento/Framework/Mail/Template/TransportBuilderByStore.php

@@ -0,0 +1,62 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+
+namespace Magento\Framework\Mail\Template;
+
+use Magento\Framework\Mail\MessageInterface;
+
+/**
+ * Class TransportBuilderByStore
+ *
+ * @deprecated The ability to set From address based on store is now available
+ * in the \Magento\Framework\Mail\Template\TransportBuilder class
+ * @see \Magento\Framework\Mail\Template\TransportBuilder::setFromByStore
+ */
+class TransportBuilderByStore
+{
+    /**
+     * Message.
+     *
+     * @var \Magento\Framework\Mail\Message
+     */
+    protected $message;
+
+    /**
+     * Sender resolver.
+     *
+     * @var \Magento\Framework\Mail\Template\SenderResolverInterface
+     */
+    private $senderResolver;
+
+    /**
+     * @param MessageInterface $message
+     * @param SenderResolverInterface $senderResolver
+     */
+    public function __construct(
+        MessageInterface $message,
+        SenderResolverInterface $senderResolver
+    ) {
+        $this->message = $message;
+        $this->senderResolver = $senderResolver;
+    }
+
+    /**
+     * Set mail from address by store.
+     *
+     * @param string|array $from
+     * @param string|int $store
+     *
+     * @return $this
+     */
+    public function setFromByStore($from, $store)
+    {
+        $result = $this->senderResolver->resolve($from, $store);
+        $this->message->clearFrom();
+        $this->message->setFrom($result['email'], $result['name']);
+
+        return $this;
+    }
+}

lib/internal/Magento/Framework/Mail/Test/Unit/Template/TransportBuilderByStoreTest.php

@@ -0,0 +1,67 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+
+namespace Magento\Framework\Mail\Test\Unit\Template;
+
+use Magento\Framework\Mail\Template\TransportBuilderByStore;
+
+class TransportBuilderByStoreTest extends \PHPUnit\Framework\TestCase
+{
+    /**
+     * @var \Magento\Framework\Mail\Template\TransportBuilderByStore
+     */
+    protected $model;
+
+    /**
+     * @var \Magento\Framework\Mail\Message | \PHPUnit_Framework_MockObject_MockObject
+     */
+    protected $messageMock;
+
+    /**
+     * @var \Magento\Framework\Mail\Template\SenderResolverInterface | \PHPUnit_Framework_MockObject_MockObject
+     */
+    protected $senderResolverMock;
+
+    /**
+     * @return void
+     */
+    protected function setUp()
+    {
+        $objectManagerHelper = new \Magento\Framework\TestFramework\Unit\Helper\ObjectManager($this);
+        $this->messageMock = $this->createMock(\Magento\Framework\Mail\Message::class);
+        $this->senderResolverMock = $this->createMock(\Magento\Framework\Mail\Template\SenderResolverInterface::class);
+
+        $this->model = $objectManagerHelper->getObject(
+            TransportBuilderByStore::class,
+            [
+                'message' => $this->messageMock,
+                'senderResolver' => $this->senderResolverMock,
+            ]
+        );
+    }
+
+    /**
+     * @return void
+     */
+    public function testSetFromByStore()
+    {
+        $sender = ['email' => '[email protected]', 'name' => 'name'];
+        $store = 1;
+        $this->senderResolverMock->expects($this->once())
+            ->method('resolve')
+            ->with($sender, $store)
+            ->willReturn($sender);
+        $this->messageMock->expects($this->once())
+            ->method('setFrom')
+            ->with('[email protected]', 'name')
+            ->willReturnSelf();
+        $this->messageMock->expects($this->once())
+            ->method('clearFrom')
+            ->willReturnSelf();
+
+        $this->model->setFromByStore($sender, $store);
+    }
+}