New: Replace SmtpClient with Mailkit

Closes #1891

(cherry picked from commit 579c4433494a848aa75abb09d78af7e98ebb96a6)

src/NzbDrone.Core/Lidarr.Core.csproj

@@ -11,6 +11,7 @@
     <PackageReference Include="FluentMigrator.Runner" Version="4.0.0-alpha.268" />
     <PackageReference Include="FluentMigrator.Runner.SQLite" Version="4.0.0-alpha.268" />
     <PackageReference Include="FluentValidation" Version="8.6.2" />
+    <PackageReference Include="MailKit" Version="2.10.1" />
     <PackageReference Include="Newtonsoft.Json" Version="12.0.3" />
     <PackageReference Include="NLog" Version="4.6.8" />
     <PackageReference Include="RestSharp" Version="106.10.1" />

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

@@ -1,7 +1,8 @@
-using System;
-using System.Net;
-using System.Net.Mail;
+using System;
+using System.Linq;
 using FluentValidation.Results;
+using MailKit.Net.Smtp;
+using MimeKit;
 using NLog;
 
 namespace NzbDrone.Core.Notifications.Email
@@ -23,25 +24,20 @@ 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));
 
-            email.To.Add(settings.To);
+            email.To.Add(MailboxAddress.Parse(settings.To));
 
             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)
             {
@@ -51,13 +47,20 @@ 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())
+            {
+                client.Connect(settings.Server, settings.Port);
+
+                if (!string.IsNullOrWhiteSpace(settings.Username))
+                {
+                    client.Authenticate(settings.Username, settings.Password);
+                }
 
-            smtp.Send(email);
+                client.Send(email);
+                client.Disconnect(true);
+            }
         }
 
         public ValidationFailure Test(EmailSettings settings)

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

@@ -31,9 +31,6 @@ 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(3, Label = "Username", Privacy = PrivacyLevel.UserName)]
         public string Username { get; set; }