diff --git a/Classes/Service/MailTemplateService.php b/Classes/Service/MailTemplateService.php
index 37b6c6f23b386996ec1425c82f4cede666f5997d..254d1f211c74e6c164bda2f132fd5d1e68983f21 100644
--- a/Classes/Service/MailTemplateService.php
+++ b/Classes/Service/MailTemplateService.php
@@ -805,47 +805,11 @@ class MailTemplateService {
 				}
 
 				$registerArray = self::writeRegisterArrayEntry(
-					$registerArray, $extensionName, $extensionKey, $templateKey, $configArray
+					$registerArray, $extensionKey, $templateKey, $configArray
 				);
 			}
 		}
 
-		//  now check for registration files with multiple templates registered
-		$registerArray = self::registerFromSingleFile($registerArray);
-		return $registerArray;
-	}
-
-	/**
-	 * Find Register.php files in all installed extensions and register the templates
-	 * These files can contain multiple template registrations and are structured as multi-dimensional arrays
-	 *
-	 * @param array $registerArray
-	 * @return array
-	 */
-	private static function registerFromSingleFile(array $registerArray) {
-		$extensionList = ExtensionManagementUtility::getLoadedExtensionListArray();
-
-		foreach ($extensionList as $extension) {
-			$extensionConfigDirectory = ExtensionManagementUtility::extPath($extension);
-			$extensionConfigDirectory .= self::CONFIG_PATH;
-
-			if (!\is_file($extensionConfigDirectory . '/' . self::REGISTER_FILE)) {
-				continue;
-			}
-
-			$configArray = (include $extensionConfigDirectory . '/' . self::REGISTER_FILE);
-
-			if ($configArray) {
-				foreach ($configArray as $key => $config) {
-					$registerArray = self::writeRegisterArrayEntry(
-						$registerArray, $config['extensionKey'], $config['extensionKey'], $config['templateKey'],
-						$config, FALSE, 'project_theme'
-					);
-				}
-			}
-
-		}
-
 		return $registerArray;
 	}
 
@@ -862,7 +826,7 @@ class MailTemplateService {
 	 * @return array
 	 */
 	private static function writeRegisterArrayEntry(
-		array $registerArray, $extensionName, $extensionKey, $templateKey, array $configArray,
+		array $registerArray, $extensionKey, $templateKey, array $configArray,
 		$transformTemplateFolder = TRUE, $storeTemplateExtension = ''
 	) {
 		// If it is not explicitly set in which extension the html should be located, use the extension set in the template settings