Using MailKit instead of SmtpClient (ORCH-267) (#8707)

* Using MailKit instead of SmtpClient

* Removing 2 more references to System.Net.Http that we hopefully don't need at all anymore

* Attempting to fix Razor compilation warning about Orchard.Email's reference to System.Net.Http

* Improving SmtpSettings.cshtml a bit (port number restrictions, user name box width)

* Fixing encription method is not persisted

* Adding migration step to migrate from EnableSsl to EncryptionMethod in SmtpSettingsPart

* Code styling/simplifications

* Using infoset default values instead of Migrations to keep SSL settings when upgrading to MailKit

---------

Co-authored-by: Lombiq <github@lombiq.com>
Co-authored-by: Benedek Farkas <benedek.farkas@lombiq.com>

src/Orchard.Tests/Orchard.Framework.Tests.csproj

@@ -133,7 +133,6 @@
       <HintPath>..\..\lib\sqlce\System.Data.SqlServerCe.dll</HintPath>
       <Private>True</Private>
     </Reference>
-    <Reference Include="System.Net.Http, Version=4.2.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" />
     <Reference Include="System.Net.Http.Formatting, Version=5.2.7.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35, processorArchitecture=MSIL">
       <HintPath>..\packages\Microsoft.AspNet.WebApi.Client.5.2.7\lib\net45\System.Net.Http.Formatting.dll</HintPath>
     </Reference>

src/Orchard.Web/Modules/Orchard.Email/Controllers/EmailAdminController.cs

@@ -40,9 +40,9 @@ namespace Orchard.Email.Controllers {
                 smtpSettings.Address = testSettings.From;
                 smtpSettings.Host = testSettings.Host;
                 smtpSettings.Port = testSettings.Port;
-                smtpSettings.EnableSsl = testSettings.EnableSsl;
+                smtpSettings.AutoSelectEncryption = testSettings.AutoSelectEncryption;
+                smtpSettings.EncryptionMethod = testSettings.EncryptionMethod;
                 smtpSettings.RequireCredentials = testSettings.RequireCredentials;
-                smtpSettings.UseDefaultCredentials = testSettings.UseDefaultCredentials;
                 smtpSettings.UserName = testSettings.UserName;
                 smtpSettings.Password = testSettings.Password;
 
@@ -64,10 +64,10 @@ namespace Orchard.Email.Controllers {
                     return Json(new { error = fakeLogger.Message });
                 }
 
-                return Json(new {status = T("Message sent.").Text});
+                return Json(new { status = T("Message sent.").Text });
             }
             catch (Exception e) {
-                return Json(new {error = e.Message});
+                return Json(new { error = e.Message });
             }
             finally {
                 var smtpChannelComponent = _smtpChannel as Component;
@@ -97,9 +97,9 @@ namespace Orchard.Email.Controllers {
             public string ReplyTo { get; set; }
             public string Host { get; set; }
             public int Port { get; set; }
-            public bool EnableSsl { get; set; }
+            public SmtpEncryptionMethod EncryptionMethod { get; set; }
+            public bool AutoSelectEncryption { get; set; }
             public bool RequireCredentials { get; set; }
-            public bool UseDefaultCredentials { get; set; }
             public string UserName { get; set; }
             public string Password { get; set; }
             public string To { get; set; }

src/Orchard.Web/Modules/Orchard.Email/Handlers/SmtpSettingsPartHandler.cs

@@ -1,12 +1,12 @@
 using System;
+using System.Configuration;
 using System.Text;
 using Orchard.ContentManagement;
-using Orchard.Email.Models;
 using Orchard.ContentManagement.Handlers;
+using Orchard.Email.Models;
 using Orchard.Localization;
 using Orchard.Logging;
 using Orchard.Security;
-using System.Configuration;
 
 namespace Orchard.Email.Handlers {
     public class SmtpSettingsPartHandler : ContentHandler {
@@ -24,7 +24,8 @@ namespace Orchard.Email.Handlers {
             OnInitializing<SmtpSettingsPart>((context, part) => {
                 part.Port = 25;
                 part.RequireCredentials = false;
-                part.EnableSsl = false;
+                part.AutoSelectEncryption = true;
+                part.EncryptionMethod = SmtpEncryptionMethod.None;
             });
         }
 

src/Orchard.Web/Modules/Orchard.Email/Migrations.cs

@@ -2,10 +2,6 @@
 
 namespace Orchard.Email {
     public class Migrations : DataMigrationImpl {
-
-        public int Create() {
-
-            return 1;
-        }
+        public int Create() => 1;
     }
 }

src/Orchard.Web/Modules/Orchard.Email/Models/SmtpEncryptionMethod.cs

@@ -0,0 +1,10 @@
+namespace Orchard.Email.Models {
+    /// <summary>
+    /// Represents an enumeration for mail encryption methods.
+    /// </summary>
+    public enum SmtpEncryptionMethod {
+        None = 0,
+        SslTls = 1,
+        StartTls = 2
+    }
+}

src/Orchard.Web/Modules/Orchard.Email/Models/SmtpSettingsPart.cs

@@ -1,7 +1,7 @@
-using System.Configuration;
+using System;
+using System.Configuration;
 using System.Net.Configuration;
 using Orchard.ContentManagement;
-using System;
 using Orchard.ContentManagement.Utilities;
 
 namespace Orchard.Email.Models {
@@ -31,9 +31,23 @@ namespace Orchard.Email.Models {
             set { this.Store(x => x.Port, value); }
         }
 
-        public bool EnableSsl {
-            get { return this.Retrieve(x => x.EnableSsl); }
-            set { this.Store(x => x.EnableSsl, value); }
+        [Obsolete($"Use {nameof(AutoSelectEncryption)} and/or {nameof(EncryptionMethod)} instead.")]
+        public bool EnableSsl => this.Retrieve(x => x.EnableSsl);
+
+        public SmtpEncryptionMethod EncryptionMethod {
+#pragma warning disable CS0618 // Type or member is obsolete
+            // Reading EnableSsl is necessary to keep the correct settings during the upgrade to MailKit.
+            get { return this.Retrieve(x => x.EncryptionMethod, EnableSsl ? SmtpEncryptionMethod.SslTls : SmtpEncryptionMethod.None); }
+#pragma warning restore CS0618 // Type or member is obsolete
+            set { this.Store(x => x.EncryptionMethod, value); }
+        }
+
+        public bool AutoSelectEncryption {
+#pragma warning disable CS0618 // Type or member is obsolete
+            // Reading EnableSsl is necessary to keep the correct settings during the upgrade to MailKit.
+            get { return this.Retrieve(x => x.AutoSelectEncryption, !EnableSsl); }
+#pragma warning restore CS0618 // Type or member is obsolete
+            set { this.Store(x => x.AutoSelectEncryption, value); }
         }
 
         public bool RequireCredentials {
@@ -41,11 +55,6 @@ namespace Orchard.Email.Models {
             set { this.Store(x => x.RequireCredentials, value); }
         }
 
-        public bool UseDefaultCredentials {
-            get { return this.Retrieve(x => x.UseDefaultCredentials); }
-            set { this.Store(x => x.UseDefaultCredentials, value); }
-        }
-
         public string UserName {
             get { return this.Retrieve(x => x.UserName); }
             set { this.Store(x => x.UserName, value); }

src/Orchard.Web/Modules/Orchard.Email/Orchard.Email.csproj

@@ -55,6 +55,12 @@
     <Prefer32Bit>false</Prefer32Bit>
   </PropertyGroup>
   <ItemGroup>
+    <Reference Include="BouncyCastle.Crypto, Version=1.9.0.0, Culture=neutral, PublicKeyToken=0e99375e54769942, processorArchitecture=MSIL">
+      <HintPath>..\..\..\packages\Portable.BouncyCastle.1.9.0\lib\net40\BouncyCastle.Crypto.dll</HintPath>
+    </Reference>
+    <Reference Include="MailKit, Version=3.1.0.0, Culture=neutral, PublicKeyToken=4e064fe7c44a8f1b, processorArchitecture=MSIL">
+      <HintPath>..\..\..\packages\MailKit.3.1.1\lib\net48\MailKit.dll</HintPath>
+    </Reference>
     <Reference Include="Microsoft.CodeDom.Providers.DotNetCompilerPlatform, Version=2.0.1.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35, processorArchitecture=MSIL">
       <HintPath>..\..\..\packages\Microsoft.CodeDom.Providers.DotNetCompilerPlatform.2.0.1\lib\net45\Microsoft.CodeDom.Providers.DotNetCompilerPlatform.dll</HintPath>
     </Reference>
@@ -62,14 +68,23 @@
     <Reference Include="Microsoft.Web.Infrastructure, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35, processorArchitecture=MSIL">
       <HintPath>..\..\..\packages\Microsoft.Web.Infrastructure.1.0.0.0\lib\net40\Microsoft.Web.Infrastructure.dll</HintPath>
     </Reference>
+    <Reference Include="MimeKit, Version=3.1.0.0, Culture=neutral, PublicKeyToken=bede1c8a46c66814, processorArchitecture=MSIL">
+      <HintPath>..\..\..\packages\MimeKit.3.1.1\lib\net48\MimeKit.dll</HintPath>
+    </Reference>
     <Reference Include="Newtonsoft.Json, Version=12.0.0.0, Culture=neutral, PublicKeyToken=30ad4fe6b2a6aeed, processorArchitecture=MSIL">
       <HintPath>..\..\..\packages\Newtonsoft.Json.12.0.3\lib\net45\Newtonsoft.Json.dll</HintPath>
     </Reference>
     <Reference Include="System" />
+    <Reference Include="System.Buffers, Version=4.0.3.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51, processorArchitecture=MSIL">
+      <HintPath>..\..\..\packages\System.Buffers.4.5.1\lib\net461\System.Buffers.dll</HintPath>
+    </Reference>
     <Reference Include="System.Configuration">
       <Private>False</Private>
     </Reference>
+    <Reference Include="System.Data" />
     <Reference Include="System.Data.DataSetExtensions" />
+    <Reference Include="System.Net.Http, Version=4.2.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" />
+    <Reference Include="System.Security" />
     <Reference Include="System.Web.ApplicationServices" />
     <Reference Include="System.Web.DynamicData" />
     <Reference Include="System.Web.Entity" />
@@ -104,6 +119,7 @@
     <Compile Include="Drivers\SmtpSettingsPartDriver.cs" />
     <Compile Include="Handlers\SmtpSettingsPartHandler.cs" />
     <Compile Include="Models\EmailMessage.cs" />
+    <Compile Include="Models\SmtpEncryptionMethod.cs" />
     <Compile Include="Models\SmtpSettingsPart.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="Rules\MailActions.cs" />
@@ -218,4 +234,4 @@
     </PropertyGroup>
     <Error Condition="!Exists('..\..\..\packages\Microsoft.CodeDom.Providers.DotNetCompilerPlatform.2.0.1\build\net46\Microsoft.CodeDom.Providers.DotNetCompilerPlatform.props')" Text="$([System.String]::Format('$(ErrorText)', '..\..\..\packages\Microsoft.CodeDom.Providers.DotNetCompilerPlatform.2.0.1\build\net46\Microsoft.CodeDom.Providers.DotNetCompilerPlatform.props'))" />
   </Target>
-</Project>
+</Project>

src/Orchard.Web/Modules/Orchard.Email/Services/MissingSettingsBanner.cs

@@ -1,5 +1,4 @@
 using System.Collections.Generic;
-using System.Net.Mail;
 using System.Web.Mvc;
 using Orchard.ContentManagement;
 using Orchard.Email.Models;
@@ -24,8 +23,8 @@ namespace Orchard.Email.Services {
 
             if (smtpSettings == null || !smtpSettings.IsValid()) {
                 var urlHelper = new UrlHelper(workContext.HttpContext.Request.RequestContext);
-                var url = urlHelper.Action("Email", "Admin", new {Area = "Settings"});
-                yield return new NotifyEntry {Message = T("The <a href=\"{0}\">SMTP settings</a> need to be configured.", url), Type = NotifyType.Warning};
+                var url = urlHelper.Action("Email", "Admin", new { Area = "Settings" });
+                yield return new NotifyEntry { Message = T("The <a href=\"{0}\">SMTP settings</a> need to be configured.", url), Type = NotifyType.Warning };
             }
         }
     }

src/Orchard.Web/Modules/Orchard.Email/Services/SmtpMessageChannel.cs

@@ -1,14 +1,17 @@
 using System;
 using System.Collections.Generic;
 using System.Configuration;
-using System.Net;
+using System.Linq;
 using System.Net.Configuration;
 using System.Net.Mail;
 using System.Web.Mvc;
+using MailKit.Security;
+using MimeKit;
 using Orchard.ContentManagement;
 using Orchard.DisplayManagement;
-using Orchard.Logging;
 using Orchard.Email.Models;
+using Orchard.Logging;
+using SmtpClient = MailKit.Net.Smtp.SmtpClient;
 
 namespace Orchard.Email.Services {
     public class SmtpMessageChannel : Component, ISmtpChannel, IDisposable {
@@ -64,67 +67,55 @@ namespace Orchard.Email.Services {
                 Content = new MvcHtmlString(emailMessage.Body)
             }));
 
-            var mailMessage = new MailMessage {
+            var mailMessage = new MimeMessage {
                 Subject = emailMessage.Subject,
-                Body = _shapeDisplay.Display(template),
-                IsBodyHtml = true
+            };
+            var mailBodyBuilder = new BodyBuilder {
+                HtmlBody = _shapeDisplay.Display(template),
             };
 
-            if (parameters.ContainsKey("Message")) {
+            if (parameters.TryGetValue("Message", out var possiblyMailMessage) && possiblyMailMessage is MailMessage legacyMessage) {
                 // A full message object is provided by the sender.
+                if (!String.IsNullOrWhiteSpace(legacyMessage.Subject)) {
+                    mailMessage.Subject = legacyMessage.Subject;
+                }
 
-                var oldMessage = mailMessage;
-                mailMessage = (MailMessage)parameters["Message"];
-
-                if (String.IsNullOrWhiteSpace(mailMessage.Subject))
-                    mailMessage.Subject = oldMessage.Subject;
-
-                if (String.IsNullOrWhiteSpace(mailMessage.Body)) {
-                    mailMessage.Body = oldMessage.Body;
-                    mailMessage.IsBodyHtml = oldMessage.IsBodyHtml;
+                if (!String.IsNullOrWhiteSpace(legacyMessage.Body)) {
+                    mailBodyBuilder.TextBody = legacyMessage.IsBodyHtml ? null : legacyMessage.Body;
+                    mailBodyBuilder.HtmlBody = legacyMessage.IsBodyHtml ? legacyMessage.Body : null;
                 }
             }
 
-            try {
+            mailMessage.Body = mailBodyBuilder.ToMessageBody();
 
-                foreach (var recipient in ParseRecipients(emailMessage.Recipients)) {
-                    mailMessage.To.Add(new MailAddress(recipient));
-                }
+            try {
+                mailMessage.To.AddRange(ParseRecipients(emailMessage.Recipients));
 
                 if (!String.IsNullOrWhiteSpace(emailMessage.Cc)) {
-                    foreach (var recipient in ParseRecipients(emailMessage.Cc)) {
-                        mailMessage.CC.Add(new MailAddress(recipient));
-                    }
+                    mailMessage.Cc.AddRange(ParseRecipients(emailMessage.Cc));
                 }
 
                 if (!String.IsNullOrWhiteSpace(emailMessage.Bcc)) {
-                    foreach (var recipient in ParseRecipients(emailMessage.Bcc)) {
-                        mailMessage.Bcc.Add(new MailAddress(recipient));
-                    }
+                    mailMessage.Bcc.AddRange(ParseRecipients(emailMessage.Bcc));
                 }
 
+                var fromAddress = default(MailboxAddress);
                 if (!String.IsNullOrWhiteSpace(emailMessage.From)) {
-                    mailMessage.From = new MailAddress(emailMessage.From);
+                    fromAddress = MailboxAddress.Parse(emailMessage.From);
                 }
                 else {
                     // Take 'From' address from site settings or web.config.
-                    mailMessage.From = !String.IsNullOrWhiteSpace(_smtpSettings.Address)
-                        ? new MailAddress(_smtpSettings.Address)
-                        : new MailAddress(((SmtpSection)ConfigurationManager.GetSection("system.net/mailSettings/smtp")).From);
+                    fromAddress = !String.IsNullOrWhiteSpace(_smtpSettings.Address)
+                        ? MailboxAddress.Parse(_smtpSettings.Address)
+                        : MailboxAddress.Parse(((SmtpSection)ConfigurationManager.GetSection("system.net/mailSettings/smtp")).From);
                 }
 
+                mailMessage.From.Add(fromAddress);
+
                 if (!String.IsNullOrWhiteSpace(emailMessage.ReplyTo)) {
-                    foreach (var recipient in ParseRecipients(emailMessage.ReplyTo)) {
-                        mailMessage.ReplyToList.Add(new MailAddress(recipient));
-                    }
-                }
-                if (parameters.ContainsKey("NotifyReadEmail")) {
-                    if (parameters["NotifyReadEmail"] is bool) {
-                        if ((bool)(parameters["NotifyReadEmail"])) {
-                            mailMessage.Headers.Add("Disposition-Notification-To", mailMessage.From.ToString());
-                        }
-                    }
+                    mailMessage.ReplyTo.AddRange(ParseRecipients(emailMessage.ReplyTo));
                 }
+
                 _smtpClientField.Value.Send(mailMessage);
             }
             catch (Exception e) {
@@ -133,26 +124,51 @@ namespace Orchard.Email.Services {
         }
 
         private SmtpClient CreateSmtpClient() {
+            var smtpConfiguration = new {
+                _smtpSettings.Host,
+                _smtpSettings.Port,
+                _smtpSettings.EncryptionMethod,
+                _smtpSettings.AutoSelectEncryption,
+                _smtpSettings.RequireCredentials,
+                _smtpSettings.UserName,
+                _smtpSettings.Password,
+            };
             // If no properties are set in the dashboard, use the web.config value.
             if (String.IsNullOrWhiteSpace(_smtpSettings.Host)) {
-                return new SmtpClient(); 
+                var smtpSection = (SmtpSection)ConfigurationManager.GetSection("system.net/mailSettings/smtp");
+                if (smtpSection.DeliveryMethod != SmtpDeliveryMethod.Network) {
+                    throw new NotSupportedException($"Only the {SmtpDeliveryMethod.Network} delivery method is supported, but "
+                        + $"{smtpSection.DeliveryMethod} delivery method is configured. Please check your Web.config.");
+                }
+
+                smtpConfiguration = new {
+                    smtpSection.Network.Host,
+                    smtpSection.Network.Port,
+                    EncryptionMethod = smtpSection.Network.EnableSsl ? SmtpEncryptionMethod.SslTls : SmtpEncryptionMethod.None,
+                    AutoSelectEncryption = !smtpSection.Network.EnableSsl,
+                    RequireCredentials = smtpSection.Network.DefaultCredentials || !String.IsNullOrWhiteSpace(smtpSection.Network.UserName),
+                    smtpSection.Network.UserName,
+                    smtpSection.Network.Password,
+                };
             }
 
-            var smtpClient = new SmtpClient {
-                UseDefaultCredentials = _smtpSettings.RequireCredentials && _smtpSettings.UseDefaultCredentials
-            };
-
-            if (!smtpClient.UseDefaultCredentials && !String.IsNullOrWhiteSpace(_smtpSettings.UserName)) {
-                smtpClient.Credentials = new NetworkCredential(_smtpSettings.UserName, _smtpSettings.Password);
+            var secureSocketOptions = SecureSocketOptions.Auto;
+            if (!smtpConfiguration.AutoSelectEncryption) {
+                secureSocketOptions = smtpConfiguration.EncryptionMethod switch {
+                    SmtpEncryptionMethod.None => SecureSocketOptions.None,
+                    SmtpEncryptionMethod.SslTls => SecureSocketOptions.SslOnConnect,
+                    SmtpEncryptionMethod.StartTls => SecureSocketOptions.StartTls,
+                    _ => SecureSocketOptions.None,
+                };
             }
 
-            if (_smtpSettings.Host != null) {
-                smtpClient.Host = _smtpSettings.Host;
+            var smtpClient = new SmtpClient();
+            smtpClient.Connect(smtpConfiguration.Host, smtpConfiguration.Port, secureSocketOptions);
+
+            if (smtpConfiguration.RequireCredentials) {
+                smtpClient.Authenticate(smtpConfiguration.UserName, smtpConfiguration.Password);
             }
 
-            smtpClient.Port = _smtpSettings.Port;
-            smtpClient.EnableSsl = _smtpSettings.EnableSsl;
-            smtpClient.DeliveryMethod = SmtpDeliveryMethod.Network;
             return smtpClient;
         }
 
@@ -160,8 +176,16 @@ namespace Orchard.Email.Services {
             return dictionary.ContainsKey(key) ? dictionary[key] as string : null;
         }
 
-        private IEnumerable<string> ParseRecipients(string recipients) {
-            return recipients.Split(new[] {',', ';'}, StringSplitOptions.RemoveEmptyEntries);
+        private IEnumerable<MailboxAddress> ParseRecipients(string recipients) {
+            return recipients.Split(new[] { ',', ';' }, StringSplitOptions.RemoveEmptyEntries)
+                .SelectMany(address => {
+                    if (MailboxAddress.TryParse(address, out var mailboxAddress)) {
+                        return new[] { mailboxAddress };
+                    }
+
+                    Logger.Error("Invalid email address: {0}", address);
+                    return Enumerable.Empty<MailboxAddress>();
+                });
         }
     }
-}
+}

src/Orchard.Web/Modules/Orchard.Email/Views/EditorTemplates/Parts/SmtpSettings.cshtml

@@ -1,4 +1,5 @@
-@using System.Net.Mail
+@using Orchard.Email.Models
+@using System.Net.Mail
 @model Orchard.Email.Models.SmtpSettingsPart
 @{
     var smtpClient = new SmtpClient();
@@ -20,15 +21,37 @@
     </div>
     <div>
         <label for="@Html.FieldIdFor(m => m.Port)">@T("Port number")</label>
-        @Html.TextBoxFor(m => m.Port, new { placeholder = smtpClient.Port, @class = "text small" })
+        @Html.TextBoxFor(m => m.Port, new { type = "number", placeholder = smtpClient.Port, min = 1, max = 65535 })
         @Html.ValidationMessage("Port", "*")
         <span class="hint">@T("The SMTP server port, usually 25.")</span>
     </div>
     <div>
-        @Html.EditorFor(m => m.EnableSsl)
-        <label for="@Html.FieldIdFor(m => m.EnableSsl)" class="forcheckbox">@T("Enable SSL communications")</label>
-        @Html.ValidationMessage("EnableSsl", "*")
-        <span class="hint">@T("Check if the SMTP server requires SSL communications.")</span>
+        <label for="@Html.FieldIdFor(m => m.EncryptionMethod)">@T("Encryption method to use")</label>
+        <select for="@Html.FieldIdFor(m => m.EncryptionMethod)"
+                id="@Html.FieldIdFor(m => m.EncryptionMethod)"
+                name="@Html.FieldNameFor(m => m.EncryptionMethod)"
+                disabled="@Model.AutoSelectEncryption">
+            @Html.SelectOption(
+                Model.EncryptionMethod,
+                SmtpEncryptionMethod.None,
+                String.Join(String.Empty, T("None").ToString(), " - ", T("Connect to server using insecure connection.").ToString()))
+            @Html.SelectOption(
+                Model.EncryptionMethod,
+                SmtpEncryptionMethod.SslTls,
+                String.Join(String.Empty, T("SSL/TLS").ToString(), " - ", T("Connect to server using SSL/TSL secure connection.").ToString()))
+            @Html.SelectOption(
+                Model.EncryptionMethod,
+                SmtpEncryptionMethod.StartTls,
+                String.Join(String.Empty, T("STARTTLS").ToString(), " - ", T("Connect to server using insecure connection and upgrade to secure using SSL/TLS.").ToString()))
+        </select>
+        @Html.ValidationMessage("EncryptionMethod", "*")
+        <span class="hint">@T("The encryption method used when connecting to mail server.")</span>
+    </div>
+    <div>
+        @Html.EditorFor(m => m.AutoSelectEncryption)
+        <label for="@Html.FieldIdFor(m => m.AutoSelectEncryption)" class="forcheckbox">@T("Auto Select Encryption method")</label>
+        @Html.ValidationMessage("AutoSelectEncryption", "*")
+        <span class="hint">@T("Check to let the system select the encryption method based on port.")</span>
     </div>
     <div>
         @Html.EditorFor(m => m.RequireCredentials)
@@ -37,32 +60,17 @@
     </div>
 
     <div data-controllerid="@Html.FieldIdFor(m => m.RequireCredentials)">
-
         <div>
-            @Html.RadioButtonFor(m => m.UseDefaultCredentials, false, new { id = "customCredentialsOption", name = "UseDefaultCredentials" })
-            <label for="customCredentialsOption" class="forcheckbox">@T("Specify username/password")</label>
-            @Html.ValidationMessage("UseDefaultCredentials", "*")
+            <label for="@Html.FieldIdFor(m => m.UserName)">@T("User name")</label>
+            @Html.TextBoxFor(m => m.UserName, new { @class = "text medium" })
+            @Html.ValidationMessage("UserName", "*")
+            <span class="hint">@T("The username for authentication.")</span>
         </div>
-
         <div>
-            @Html.RadioButtonFor(m => m.UseDefaultCredentials, true, new { id = "defaultCredentialsOptions", name = "UseDefaultCredentials" })
-            <label for="defaultCredentialsOptions" class="forcheckbox">@T("Use Windows authentication")</label>
-            @Html.ValidationMessage("UseDefaultCredentials", "*")
-            <span class="hint">@T("When this option is selected, the aplication pool or host-process identity is used to authenticate with the mail server. ")</span>
-        </div>
-        <div class="options">
-            <span data-controllerid="customCredentialsOption">
-                <label for="@Html.FieldIdFor(m => m.UserName)">@T("User name")</label>
-                @Html.TextBoxFor(m => m.UserName, new { @class = "text" })
-                @Html.ValidationMessage("UserName", "*")
-                <span class="hint">@T("The username for authentication.")</span>
-            </span>
-            <span data-controllerid="customCredentialsOption">
-                <label for="@Html.FieldIdFor(m => m.Password)">@T("Password")</label>
-                @Html.TextBoxFor(m => m.Password, new { type = "password", @class = "text medium" })
-                @Html.ValidationMessage("Password", "*")
-                <span class="hint">@T("The password for authentication.")</span>
-            </span>
+            <label for="@Html.FieldIdFor(m => m.Password)">@T("Password")</label>
+            @Html.TextBoxFor(m => m.Password, new { type = "password", @class = "text medium" })
+            @Html.ValidationMessage("Password", "*")
+            <span class="hint">@T("The password for authentication.")</span>
         </div>
     </div>
 </fieldset>
@@ -106,9 +114,9 @@
                     from = $("#@Html.FieldIdFor(m => m.Address)"),
                     host = $("#@Html.FieldIdFor(m => m.Host)"),
                     port = $("#@Html.FieldIdFor(m => m.Port)"),
-                    enableSsl = $("#@Html.FieldIdFor(m => m.EnableSsl)"),
+                    encryptionMethod = $("#@Html.FieldIdFor(m => m.EncryptionMethod)"),
+                    autoSelectEncryption = $("#@Html.FieldIdFor(m => m.AutoSelectEncryption)"),
                     requireCredentials = $("#@Html.FieldIdFor(m => m.RequireCredentials)"),
-                    useDefaultCredentials = $("input[name='@Html.NameFor(m => m.UseDefaultCredentials)']"),
                     userName = $("#@Html.FieldIdFor(m => m.UserName)"),
                     password = $("#@Html.FieldIdFor(m => m.Password)"),
                     to = $("#emailtestto"),
@@ -123,9 +131,9 @@
                         from: from.val(),
                         host: host.val(),
                         port: port.val(),
-                        enableSsl: enableSsl.prop("checked"),
+                        encryptionMethod: encryptionMethod.val(),
+                        autoSelectEncryption: autoSelectEncryption.prop("checked"),
                         requireCredentials: requireCredentials.prop("checked"),
-                        useDefaultCredentials: useDefaultCredentials.filter(':checked').val(),
                         userName: userName.val(),
                         password: password.val(),
                         to: to.val(),

src/Orchard.Web/Modules/Orchard.Email/Web.config

@@ -29,6 +29,7 @@
         <compilation targetFramework="4.8">
             <assemblies>
                 <add assembly="System.Core, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089" />
+                <add assembly="System.Net.Http, Version=4.2.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" />
                 <add assembly="System.Web.Abstractions, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" />
                 <add assembly="System.Web.Routing, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" />
                 <add assembly="System.Data.Linq, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089" />

src/Orchard.Web/Modules/Orchard.Email/packages.config

@@ -1,9 +1,13 @@
 <?xml version="1.0" encoding="utf-8"?>
 <packages>
+  <package id="MailKit" version="3.1.1" targetFramework="net48" />
   <package id="Microsoft.AspNet.Mvc" version="5.2.7" targetFramework="net48" />
   <package id="Microsoft.AspNet.Razor" version="3.2.7" targetFramework="net48" />
   <package id="Microsoft.AspNet.WebPages" version="3.2.7" targetFramework="net48" />
   <package id="Microsoft.CodeDom.Providers.DotNetCompilerPlatform" version="2.0.1" targetFramework="net48" />
   <package id="Microsoft.Web.Infrastructure" version="1.0.0.0" targetFramework="net48" />
+  <package id="MimeKit" version="3.1.1" targetFramework="net48" />
   <package id="Newtonsoft.Json" version="12.0.3" targetFramework="net48" />
-</packages>
+  <package id="Portable.BouncyCastle" version="1.9.0" targetFramework="net48" />
+  <package id="System.Buffers" version="4.5.1" targetFramework="net48" />
+</packages>