7 files declare their use of SmsMessageEvent in SMS Framework 2.1.x

DefaultSmsProvider.php in src/Provider/DefaultSmsProvider.php

Memory.php in tests/modules/sms_test_gateway/src/Plugin/SmsGateway/Memory.php

SmsEventSubscriber.php in modules/sms_user/src/EventSubscriber/SmsEventSubscriber.php

SmsIncomingEventInterface.php in src/Plugin/SmsGateway/SmsIncomingEventInterface.php

SmsIncomingEventProcessorInterface.php in src/Plugin/SmsGateway/SmsIncomingEventProcessorInterface.php

SmsMessageProcessor.php in src/EventSubscriber/SmsMessageProcessor.php

SmsTestGatewayEventSubscriber.php in tests/modules/sms_test_gateway/src/EventSubscriber/SmsTestGatewayEventSubscriber.php