diff --git a/composer.json b/composer.json
index b119f099..4f86b78d 100644
--- a/composer.json
+++ b/composer.json
@@ -31,7 +31,6 @@
     "require": {
         "php": "^5.6 || ^7.0",
         "ext-iconv": "*",
-        "laminas/laminas-loader": "^2.5",
         "laminas/laminas-mime": "^2.5",
         "laminas/laminas-stdlib": "^2.7 || ^3.0",
         "laminas/laminas-validator": "^2.10.2",
diff --git a/src/Header/HeaderLoader.php b/src/Header/HeaderLoader.php
index 026c5c15..d9996a31 100644
--- a/src/Header/HeaderLoader.php
+++ b/src/Header/HeaderLoader.php
@@ -8,12 +8,10 @@
 
 namespace Laminas\Mail\Header;
 
-use Laminas\Loader\PluginClassLoader;
-
 /**
  * Plugin Class Loader implementation for HTTP headers
  */
-class HeaderLoader extends PluginClassLoader
+class HeaderLoader
 {
     /**
      * @var array Pre-aliased Header plugins
@@ -46,4 +44,39 @@ class HeaderLoader extends PluginClassLoader
         'subject'                   => Subject::class,
         'to'                        => To::class,
     ];
+
+    /**
+     * @param string $name
+     * @param string|null $default
+     * @return string|null
+     */
+    public function get($name, $default = null)
+    {
+        $name = $this->normalizeName($name);
+        return isset($this->headerClassMap[$name]) ? $this->headerClassMap[$name] : $default;
+    }
+
+    /**
+     * @param string $name
+     * @return bool
+     */
+    public function has($name)
+    {
+        return isset($this->headerClassMap[$this->normalizeName($name)]);
+    }
+
+    public function add($name, $class)
+    {
+        $this->headerClassMap[$this->normalizeName($name)] = $class;
+    }
+
+    public function remove($name)
+    {
+        unset($this->headerClassMap[$this->normalizeName($name)]);
+    }
+
+    private function normalizeName($name)
+    {
+        return strtolower($name);
+    }
 }
diff --git a/src/Headers.php b/src/Headers.php
index fb57d201..e561ec85 100644
--- a/src/Headers.php
+++ b/src/Headers.php
@@ -11,7 +11,6 @@
 use ArrayIterator;
 use Countable;
 use Iterator;
-use Laminas\Loader\PluginClassLocator;
 use Laminas\Mail\Header\GenericHeader;
 use Laminas\Mail\Header\HeaderInterface;
 use Traversable;
@@ -30,9 +29,9 @@ class Headers implements Countable, Iterator
     const FOLDING = "\r\n ";
 
     /**
-     * @var \Laminas\Loader\PluginClassLoader
+     * @var Header\HeaderLoader
      */
-    protected $pluginClassLoader = null;
+    protected $headerLoader = null;
 
     /**
      * @var array key names for $headers array
@@ -118,31 +117,6 @@ public static function fromString($string, $EOL = self::EOL)
         return $headers;
     }
 
-    /**
-     * Set an alternate implementation for the PluginClassLoader
-     *
-     * @param  PluginClassLocator $pluginClassLoader
-     * @return Headers
-     */
-    public function setPluginClassLoader(PluginClassLocator $pluginClassLoader)
-    {
-        $this->pluginClassLoader = $pluginClassLoader;
-        return $this;
-    }
-
-    /**
-     * Return an instance of a PluginClassLocator, lazyload and inject map if necessary
-     *
-     * @return PluginClassLocator
-     */
-    public function getPluginClassLoader()
-    {
-        if ($this->pluginClassLoader === null) {
-            $this->pluginClassLoader = new Header\HeaderLoader();
-        }
-        return $this->pluginClassLoader;
-    }
-
     /**
      * Set the header encoding
      *
@@ -481,7 +455,7 @@ public function loadHeader($headerLine)
         list($name, ) = Header\GenericHeader::splitHeaderLine($headerLine);
 
         /** @var HeaderInterface $class */
-        $class = $this->getPluginClassLoader()->load($name) ?: Header\GenericHeader::class;
+        $class = $this->resolveHeaderClass($name);
         return $class::fromString($headerLine);
     }
 
@@ -496,7 +470,7 @@ protected function lazyLoadHeader($index)
         $key   = $this->headersKeys[$index];
 
         /** @var GenericHeader $class */
-        $class = ($this->getPluginClassLoader()->load($key)) ?: Header\GenericHeader::class;
+        $class = $this->resolveHeaderClass($key);
 
         $encoding = $current->getEncoding();
         $headers  = $class::fromString($current->toString());
@@ -528,4 +502,17 @@ protected function normalizeFieldName($fieldName)
     {
         return str_replace(['-', '_', ' ', '.'], '', strtolower($fieldName));
     }
+
+    /**
+     * @param string $key
+     * @return string
+     */
+    private function resolveHeaderClass($key)
+    {
+        if ($this->headerLoader === null) {
+            $this->headerLoader = new Header\HeaderLoader();
+        }
+
+        return $this->headerLoader->get($key, Header\GenericHeader::class);
+    }
 }
diff --git a/test/Header/HeaderLoaderTest.php b/test/Header/HeaderLoaderTest.php
new file mode 100644
index 00000000..dd553e1c
--- /dev/null
+++ b/test/Header/HeaderLoaderTest.php
@@ -0,0 +1,102 @@
+<?php
+
+/**
+ * @see       https://github.com/laminas/laminas-mail for the canonical source repository
+ * @copyright https://github.com/laminas/laminas-mail/blob/master/COPYRIGHT.md
+ * @license   https://github.com/laminas/laminas-mail/blob/master/LICENSE.md New BSD License
+ */
+
+namespace LaminasTest\Mail\Header;
+
+use PHPUnit\Framework\TestCase;
+use Laminas\Mail\Header;
+
+class HeaderLoaderTest extends TestCase
+{
+    /**
+     * @var Header\HeaderLoader
+     */
+    private $headerLoader;
+
+    public function setUp()
+    {
+        $this->headerLoader = new Header\HeaderLoader();
+    }
+
+    public function provideHeaderNames()
+    {
+        return [
+            'with existing name' => ['to', Header\To::class],
+            'with non-existent name' => ['foo', null],
+            'with default value' => ['foo', Header\GenericHeader::class, Header\GenericHeader::class],
+        ];
+    }
+
+    /**
+     * @param $name
+     * @param $expected
+     * @param $default
+     * @dataProvider provideHeaderNames
+     */
+    public function testHeaderIsProperlyLoaded($name, $expected, $default = null)
+    {
+        $this->assertEquals($expected, $this->headerLoader->get($name, $default));
+    }
+
+    public function testHeaderExistenceIsProperlyChecked()
+    {
+        $this->assertTrue($this->headerLoader->has('to'));
+        $this->assertTrue($this->headerLoader->has('To'));
+        $this->assertTrue($this->headerLoader->has('Reply_to'));
+        $this->assertTrue($this->headerLoader->has('SUBJECT'));
+        $this->assertFalse($this->headerLoader->has('foo'));
+        $this->assertFalse($this->headerLoader->has('bar'));
+    }
+
+    public function testHeaderCanBeAdded()
+    {
+        $this->assertFalse($this->headerLoader->has('foo'));
+        $this->headerLoader->add('foo', Header\GenericHeader::class);
+        $this->assertTrue($this->headerLoader->has('foo'));
+    }
+
+    public function testHeaderCanBeRemoved()
+    {
+        $this->assertTrue($this->headerLoader->has('to'));
+        $this->headerLoader->remove('to');
+        $this->assertFalse($this->headerLoader->has('to'));
+    }
+
+    public static function expectedHeaders()
+    {
+        return [
+            ['bcc', Header\Bcc::class],
+            ['cc', Header\Cc::class],
+            ['contenttype', Header\ContentType::class],
+            ['content_type', Header\ContentType::class],
+            ['content-type', Header\ContentType::class],
+            ['date', Header\Date::class],
+            ['from', Header\From::class],
+            ['mimeversion', Header\MimeVersion::class],
+            ['mime_version', Header\MimeVersion::class],
+            ['mime-version', Header\MimeVersion::class],
+            ['received', Header\Received::class],
+            ['replyto', Header\ReplyTo::class],
+            ['reply_to', Header\ReplyTo::class],
+            ['reply-to', Header\ReplyTo::class],
+            ['sender', Header\Sender::class],
+            ['subject', Header\Subject::class],
+            ['to', Header\To::class],
+        ];
+    }
+
+    /**
+     * @dataProvider expectedHeaders
+     * @param $name
+     * @param $class
+     */
+    public function testDefaultHeadersMapResolvesProperHeader($name, $class)
+    {
+        $this->assertEquals($class, $this->headerLoader->get($name));
+    }
+}
\ No newline at end of file
diff --git a/test/HeadersTest.php b/test/HeadersTest.php
index c747feb9..2b483e23 100644
--- a/test/HeadersTest.php
+++ b/test/HeadersTest.php
@@ -117,10 +117,7 @@ public function testPluginClassLoaderAccessors()
     public function testHeadersFromStringMultiHeaderWillAggregateLazyLoadedHeaders()
     {
         $headers = new Mail\Headers();
-        /* @var $pcl \Laminas\Loader\PluginClassLoader */
-        $pcl = $headers->getPluginClassLoader();
-        $pcl->registerPlugin('foo', GenericMultiHeader::class);
-        $headers->addHeaderLine('foo: bar1,bar2,bar3');
+        $headers->addHeaderLine('foo', ['bar1@domain.com', 'bar2@domain.com', 'bar3@domain.com']);
         $headers->forceLoading();
         $this->assertEquals(3, $headers->count());
     }
@@ -409,40 +406,6 @@ public function testToArrayFormatEncoded()
         $this->assertEquals($expected, $array);
     }
 
-    public static function expectedHeaders()
-    {
-        return [
-            ['bcc', Header\Bcc::class],
-            ['cc', Header\Cc::class],
-            ['contenttype', Header\ContentType::class],
-            ['content_type', Header\ContentType::class],
-            ['content-type', Header\ContentType::class],
-            ['date', Header\Date::class],
-            ['from', Header\From::class],
-            ['mimeversion', Header\MimeVersion::class],
-            ['mime_version', Header\MimeVersion::class],
-            ['mime-version', Header\MimeVersion::class],
-            ['received', Header\Received::class],
-            ['replyto', Header\ReplyTo::class],
-            ['reply_to', Header\ReplyTo::class],
-            ['reply-to', Header\ReplyTo::class],
-            ['sender', Header\Sender::class],
-            ['subject', Header\Subject::class],
-            ['to', Header\To::class],
-        ];
-    }
-
-    /**
-     * @dataProvider expectedHeaders
-     */
-    public function testDefaultPluginLoaderIsSeededWithHeaders($plugin, $class)
-    {
-        $headers = new Mail\Headers();
-        $loader  = $headers->getPluginClassLoader();
-        $test    = $loader->load($plugin);
-        $this->assertEquals($class, $test);
-    }
-
     public function testClone()
     {
         $headers = new Mail\Headers();