Mail notifications don't work when implementing IEmailNotificationType plugin interface

I am trying to add support for notification (live, email) using INotificationType, IEmailNotificationType interfaces.

Live notifications are working, the GetMessage method is called to create a message and I see live toast.

IEmailNotificationType.Get method is not called for me.

Using a simple source code example, where after creating a media gallery item, the user should receive a notifications (email, live).

Code example:

using System;
using Telligent.Common;
using Telligent.Evolution.Extensibility;
using Telligent.Evolution.Extensibility.Api.Version1;
using Telligent.Evolution.Extensibility.Content.Version1;
using Telligent.Evolution.Extensibility.Email.Version1;

namespace SE.Notifications
{
    public class MyNotificationPlugin : INotificationType, IEmailNotificationType
    {
        public string NotificationTypeName => "MyNotificationTypeName";

        public string NotificationTypeDescription => "MyNotificationTypeDescription";

        public string NotificationTypeCategory => "MyNotificationTypeCategory";

        private readonly Guid m_NotificationGuid = new Guid("a0e161f7-7609-46df-be04-0a7deb237e89");

        public Guid NotificationTypeId => m_NotificationGuid;

        public bool IsCacheable => true;

        public bool VaryCacheByUser => true;

        public string Name => "My Notification Plugin";

        public string Description => string.Empty;

        private INotificationController m_Controller;

        public bool CanDeleteNotification(Guid notificationId, int userId)
        {
            var notification = Apis.Get<INotifications>().Get(notificationId);
            return notification != null && notification.UserId == userId;
        }

        public string GetTargetUrl(Guid notificationId)
        {
            var notification = Apis.Get<INotifications>().Get(notificationId);
            return notification != null && notification.Content != null ? notification.Content.Url : null;
        }

        public void Initialize()
        {
            var media = Apis.Get<IMedia>();
            media.Events.AfterCreate += Events_AfterCreate;
        }

        public void SetController(INotificationController controller)
        {
            m_Controller = controller;
        }

        private void Events_AfterCreate(MediaAfterCreateEventArgs e)
        {
            var media = Apis.Get<IMedia>();


            m_Controller.CreateUpdate(new NotificationCreateUpdateOptions
            {
                ContentId = e.ContentId,
                ContentTypeId = media.ContentTypeId,
                LastUpdate = DateTime.UtcNow,
                UserId = e.Author.Id.Value,
                ActorIdToAdd = e.Author.Id
            });
        }



        public string GetMessage(Guid notificationId, string target)
        {
            var eventLogger = Services.Get<IEventLog>();
            eventLogger.Write("Live message sent", new EventLogEntryWriteOptions() { EventType = "Information", Category = "Notification Test" });

            return "Live Message";
        }

        public string Get(EmailTarget target, Telligent.Evolution.Extensibility.Api.Entities.Version1.Notification notification)
        {

            // NOTE: This method is never called

            var eventLogger = Services.Get<IEventLog>();
            eventLogger.Write("Mail template creating", new EventLogEntryWriteOptions() { EventType = "Information", Category = "Notification Test" });

            // TODO: create working template
            return "My Mail Template";
        }
    }
}

Email options (SMTP) - enabled and configured.
User has "private & public emails", "Enable email contact" - enabled.
"Live Alert" and "Email" enabled on Profile => Settings => Notifications page.
Any "Send preview email" notifications in the Administration panel are working for me and I receiving emails.
Version: 11.1.0.9731 (Developer mode)