6 files declare their use of EmailWebformHandler in Webform 6.x

ScheduleEmailWebformHandler.php in modules/webform_scheduled_email/src/Plugin/WebformHandler/ScheduleEmailWebformHandler.php

webform.install.update.inc in includes/webform.install.update.inc

Archived Webform update hooks.

webform.maillog.inc in third_party_settings/webform.maillog.inc

Integrates third party settings on the Maillog module's behalf.

WebformTestController.php in src/Controller/WebformTestController.php

WebformTranslationConfigManager.php in src/WebformTranslationConfigManager.php

webform_group.module in modules/webform_group/webform_group.module

Provides a Webform integration with the Group module.