Replace SmtpClient with Mailkit

src/NzbDrone.Core/Notifications/Email/EmailService.cs

@@ -1,8 +1,9 @@
 using System;
 using System.Linq;
-using System.Net;
-using System.Net.Mail;
 using FluentValidation.Results;
+using MailKit.Net.Smtp;
+using MailKit.Security;
+using MimeKit;
 using NLog;
 
 namespace NzbDrone.Core.Notifications.Email
@@ -24,27 +25,22 @@ namespace NzbDrone.Core.Notifications.Email
 
         public void SendEmail(EmailSettings settings, string subject, string body, bool htmlBody = false)
         {
-            var email = new MailMessage();
-            email.From = new MailAddress(settings.From);
+            var email = new MimeMessage();
+            email.From.Add(MailboxAddress.Parse(settings.From));
 
-            settings.To.ToList().ForEach(x => email.To.Add(x));
-            settings.CC.ToList().ForEach(x => email.CC.Add(x));
-            settings.Bcc.ToList().ForEach(x => email.Bcc.Add(x));
+            settings.To.ToList().ForEach(x => email.To.Add(MailboxAddress.Parse(x)));
+            settings.CC.ToList().ForEach(x => email.Cc.Add(MailboxAddress.Parse(x)));
+            settings.Bcc.ToList().ForEach(x => email.Bcc.Add(MailboxAddress.Parse(x)));
 
             email.Subject = subject;
-            email.Body = body;
-            email.IsBodyHtml = htmlBody;
-
-            NetworkCredential credentials = null;
-
-            if (!string.IsNullOrWhiteSpace(settings.Username))
+            email.Body = new TextPart(htmlBody ? "html" : "plain")
             {
-                credentials = new NetworkCredential(settings.Username, settings.Password);
-            }
+                Text = body
+            };
 
             try
             {
-                Send(email, settings.Server, settings.Port, settings.Ssl, credentials);
+                Send(email, settings);
             }
             catch (Exception ex)
             {
@@ -54,13 +50,34 @@ namespace NzbDrone.Core.Notifications.Email
             }
         }
 
-        private void Send(MailMessage email, string server, int port, bool ssl, NetworkCredential credentials)
+        private void Send(MimeMessage email, EmailSettings settings)
         {
-            var smtp = new SmtpClient(server, port);
-            smtp.EnableSsl = ssl;
-            smtp.Credentials = credentials;
+            using (var client = new SmtpClient())
+            {
+                var serverOption = SecureSocketOptions.Auto;
 
-            smtp.Send(email);
+                if (settings.RequireEncryption)
+                {
+                    if (settings.Port == 465)
+                    {
+                        serverOption = SecureSocketOptions.SslOnConnect;
+                    }
+                    else
+                    {
+                        serverOption = SecureSocketOptions.StartTls;
+                    }
+                }
+
+                client.Connect(settings.Server, settings.Port, serverOption);
+
+                if (!string.IsNullOrWhiteSpace(settings.Username))
+                {
+                    client.Authenticate(settings.Username, settings.Password);
+                }
+
+                client.Send(email);
+                client.Disconnect(true);
+            }
         }
 
         public ValidationFailure Test(EmailSettings settings)

src/NzbDrone.Core/Notifications/Email/EmailSettings.cs

@@ -34,7 +34,6 @@ namespace NzbDrone.Core.Notifications.Email
         {
             Server = "smtp.gmail.com";
             Port = 587;
-            Ssl = true;
 
             To = Array.Empty<string>();
             CC = Array.Empty<string>();
@@ -47,8 +46,8 @@ namespace NzbDrone.Core.Notifications.Email
         [FieldDefinition(1, Label = "Port")]
         public int Port { get; set; }
 
-        [FieldDefinition(2, Label = "SSL", Type = FieldType.Checkbox)]
-        public bool Ssl { get; set; }
+        [FieldDefinition(2, Label = "Require Encryption", HelpText = "Require SSL (Port 465 only) or StartTLS (any other port)", Type = FieldType.Checkbox)]
+        public bool RequireEncryption { get; set; }
 
         [FieldDefinition(3, Label = "Username", Privacy = PrivacyLevel.UserName)]
         public string Username { get; set; }

src/NzbDrone.Core/Prowlarr.Core.csproj

@@ -4,6 +4,7 @@
   </PropertyGroup>
   <ItemGroup>
     <PackageReference Include="Dapper" Version="2.0.78" />
+    <PackageReference Include="MailKit" Version="2.10.1" />
     <PackageReference Include="System.Memory" Version="4.5.4" />
     <PackageReference Include="System.ServiceModel.Syndication" Version="5.0.0" />
     <PackageReference Include="FluentMigrator.Runner" Version="4.0.0-alpha.268" />