11 files declare their use of MassContactInterface in Mass Contact 8

AdminSettingsForm.php in src/Form/AdminSettingsForm.php

AdminSettingsFormTest.php in src/Tests/Form/AdminSettingsFormTest.php

EmailBodyForm.php in src/Form/EmailBodyForm.php

MassContactForm.php in src/Form/MassContactForm.php

MassContactFormTest.php in tests/src/Functional/Form/MassContactFormTest.php

MassContactMessageConfirmForm.php in src/Form/MassContactMessageConfirmForm.php

mass_contact.install in ./mass_contact.install

Install hooks for the mass contact module.

mass_contact.module in ./mass_contact.module

This is the main code file for the Mass Contact module.

OptOutTest.php in tests/src/Kernel/OptOutTest.php

QueueMessages.php in src/Plugin/QueueWorker/QueueMessages.php

SendMessage.php in src/Plugin/QueueWorker/SendMessage.php