SocialPub/PrivaPub/Services/Mailer.cs

using MailKit.Net.Smtp;

using Microsoft.Extensions.Options;

using MimeKit;

using PrivaPub.Models;

namespace PrivaPub.Services
{
	public interface IMailer
	{
		/// <summary>Sends a plain-text email; throws when SMTP fails, so the job that sends it retries.</summary>
		Task Send(string to, string subject, string body, CancellationToken token);
	}

	// The server's one way to send an email: through the SMTP account in appsettings (AppConfiguration:EmailConfiguration),
	// read as it is now. Only jobs call it, so nobody waits on SMTP.
	public class Mailer : IMailer
	{
		readonly IOptionsMonitor<AppConfiguration> _app;
		readonly Domain.Instance.IInstanceSettings _settings;

		public Mailer(IOptionsMonitor<AppConfiguration> app, Domain.Instance.IInstanceSettings settings)
		{
			_app = app;
			_settings = settings;
		}

		public async Task Send(string to, string subject, string body, CancellationToken token)
		{
			var email = _app.CurrentValue.EmailConfiguration;
			var message = new MimeMessage();
			message.From.Add(new MailboxAddress(_settings.Current.Title, email.SmtpUsername));//the server's name, as its administrator set it
			message.To.Add(MailboxAddress.Parse(to));
			message.Subject = subject;
			message.Body = new TextPart("plain") { Text = body };
			using var smtp = new SmtpClient();
			await smtp.ConnectAsync(email.SmtpServer, email.SmtpPort, email.UseSSL, token);
			if (!string.IsNullOrEmpty(email.SmtpPassword))
				await smtp.AuthenticateAsync(email.SmtpUsername, email.SmtpPassword, token);
			await smtp.SendAsync(message, token);
			await smtp.DisconnectAsync(quit: true, token);
		}
	}
}