Adding a signature looks like this:

// C#

using (RSACryptoServiceProvider rsa = new RSACryptoServiceProvider())
{
   IMail email = Mail
       .Text("text")
       .From("alice@mail.com")
       .To("bob@mail.com")
       .Subject("subject")
       .DKIMSign(rsa, "brisbane", "example.com")
       .Create();
}

' VB.NET

Using rsa As New RSACryptoServiceProvider()
	Dim email As IMail = Mail _
		.Text("text") _
		.From("alice@mail.com") _
		.[To]("bob@mail.com") _
		.Subject("subject") _
		.DKIMSign(rsa, "brisbane", "example.com") _
		.Create()
End Using

So what you need is RSACryptoServiceProvider with your private key, and two strings: selector and domain.

Basically how this works is the recipient of the email queries the DNS server for TXT record for selector._domainkey.domain (in our sample it is: “brisbane._domainkey.example.com”) to get the public key and validate the signature.

You can use nslookup to get the public key for a domain:

Microsoft Windows [Version 6.1.7600]
Copyright (c) 2009 Microsoft Corporation.  All rights reserved.

C:\Users\Pawel>nslookup
Default Server:  UnKnown
Address:  192.168.0.1

> set type=TXT
> gamma._domainkey.gmail.com
Server:  UnKnown
Address:  192.168.0.1

Non-authoritative answer:
gamma._domainkey.gmail.com      text =

        "k=rsa; t=y; p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDIhyR3oItOy22ZOaBrI
Ve9m/iME3RqOJeasANSpg2YTHTYV+Xtp4xwf5gTjCmHQEMOs0qYu0FYiNQPQogJ2t0Mfx9zNu06rfRBD
jiIU9tpx2T+NGlWZ8qhbiLo5By8apJavLyqTLavyPSrvsx0B3YzC63T4Age2CDqZYA+OwSMWQIDAQAB"

gmail.com       nameserver = ns1.google.com
gmail.com       nameserver = ns4.google.com
gmail.com       nameserver = ns3.google.com
gmail.com       nameserver = ns2.google.com
ns1.google.com  internet address = 216.239.32.10
ns2.google.com  internet address = 216.239.34.10
ns3.google.com  internet address = 216.239.36.10
ns4.google.com  internet address = 216.239.38.10
>

But don’t worry as Mail.dll will make this DNS query for you.

Validating (including DNS query for public key) is simple:

// C#

IMail email = new MailBuilder()
    .CreateFromEmlFile("signed_gamma.gmail.eml");
bool isValid = email.CheckDKIMSignature();

' VB.NET

Dim email As IMail = New MailBuilder() _
    .CreateFromEmlFile("signed_gamma.gmail.eml")
Dim isValid As Boolean = email.CheckDKIMSignature()

You can download Mail.dll .NET email component here.

// C#

client.Connect("imap.example.com");

' VB.NET

client.Connect("imap.example.com");

Then, before logging-in, start implicit SSL negotiation. The command name differs for different protocols:

In case of IMAP:

// C#

client.StartTLS();

' VB.NET

client.StartTLS()

In case of POP3:

// C#

client.STLS();

' VB.NET

client.STLS()

In case of SMTP:

// C#

client.StartTLS();

' VB.NET

client.StartTLS()

Now, your connection is secured.

Remember that you can ignore SSL certificate errors using ServerCertificateValidate event:

// C#

client.ServerCertificateValidate +=
    (sender, e) => { e.IsValid = true; };

' VB.NET

client.ServerCertificateValidate += Function(sender, e) Do
	e.IsValid = True
End Function

Mail.dll .NET IMAP client allows you to download only needed parts of the specified message.

First you need to get the structure of the message.
There are two methods for that: GetBodyStructureByUID and GetBodyStructure.

BodyStructure contains information about plain text, html, and all attachments of the message. It does not contain any data though.

To download text parts of the email (like html or plain text) you can use: GetMimePartTextByUID or GetMimePartText.

To download attachments use: GetMimePartByUID or GetMimePart.

Here’s the full sample for this feature:

// C#

using(Imap imap = new Imap())
{
	imap.Connect("imap.server.com");
	imap.Login("user", "password");

	imap.SelectInbox();
	List<long> uidList = imap.SearchFlag(Flag.Unseen);
	foreach (long uid in uidList)
	{
		// Get the structure of the email
		BodyStructure structure = imap.GetBodyStructureByUID(uid);

		// Download only text and html parts
		string text = imap.GetMimePartTextByUID(uid, structure.Text);
		string html = imap.GetMimePartTextByUID(uid, structure.Html);

		Console.WriteLine(text);
		Console.WriteLine(html);

		// Show all attachments' filenames
		foreach(MimeStructure attachment in structure.Attachments)
		{
			Console.WriteLine(attachment.FileName);
			// You can also download entire attachment
			byte[] bytes = imap.GetMimePartByUID(uid, attachment);
		}
	}
	imap.Close(true);
}

' VB.NET

Using imap As New Imap()
	imap.Connect("imap.server.com")
	imap.Login("user", "password")

	imap.SelectInbox()
	Dim uidList As List(Of Long) = imap.SearchFlag(Flag.Unseen)
	For Each uid As Long In uidList
		' Get the structure of the email
		Dim struct As BodyStructure = imap.GetBodyStructureByUID(uid)

		' Download only text and html parts
		Dim text As String = imap.GetMimePartTextByUID(
			uid, struct.Text)
		Dim html As String = imap.GetMimePartTextByUID(
			uid, struct.Html)

		Console.WriteLine(text)
		Console.WriteLine(html)

		' Show all attachments' filenames
		For Each attachment As MimeStructure In struct.Attachments
			Console.WriteLine(attachment.FileName)
			' You can also download entire attachment
			Dim bytes As Byte() = imap.GetMimePartByUID(
				uid, attachment)
		Next
	Next
	imap.Close(True)
End Using

If you don’t want this behavior, there are two things you can do.

First is to use Examine method instead of Select:

// C#

using(Imap imap = new Imap())
{
    imap.Connect("imap.server.com");
    imap.Login("user", "password");

    imap.ExamineInbox(); // -or- imap.Examine("Inbox");

    // ...

    imap.Close(true);
}

' VB.NET

Using imap As New Imap
    imap.Connect("imap.server.com")
    imap.Login("user", "password")

    imap.SelectInbox()

    imap.ExamineInbox() ' -or- imap.Examine("Inbox")

    ' ...

    imap.Close(True)
End Using

Examine puts mailbox (also called folder) into read-only state, so no \Seen flag is added.
The drawback is that you can not delete a message.

Second approach is to use one of the Peek methods on the IMAP client:

// C#

using(Imap imap = new Imap())
{
    imap.Connect("imap.server.com");
    imap.Login("user", "password");

    imap.SelectInbox();
    List<long> uidList = imap.SearchFlag(Flag.Unseen);
    foreach (long uid in uidList)
    {
        IMail email = new MailBuilder()
            .CreateFromEml(imap.PeekMessageByUID(uid));
        Console.WriteLine(email.Subject);
    }
    imap.Close(true);
}

' VB.NET

Using imap As New Imap
    imap.Connect("imap.server.com")
    imap.Login("user", "password")

    imap.SelectInbox()
    Dim uidList As List(Of Long) = imap.SearchFlag(Flag.Unseen)

    For Each uid As Long In uidList
        Dim email As IMail = New MailBuilder() _
            .CreateFromEml(imap.PeekMessageByUID(uid))
        Console.WriteLine(email.Subject)
    Next
    imap.Close(True)
End Using

There are Peek methods for downloading headers and even parts of the email message.

You can download Mail.dll IMAP client here.

In this post I’ll show how to access GMail account using OAuth authentication method. The key advantage of this method is that it allows an application to access users email without knowing user’s password.

You can read more on OAuth authentication with Google accounts here:
http://code.google.com/apis/accounts/docs/OAuth_ref.html

Gmail IMAP and SMTP using OAuth:
http://code.google.com/apis/gmail/oauth/protocol.html

If your application is not registered, please select HMAC-SHA1 and use the following key and secret:
consumer key: “anonymous”
consumer secret: “anonymous”

You can manage your domains here:
https://www.google.com/accounts/ManageDomains

The following code makes several HTTP requests to authenticate your application. It also fires up the web browser, so the user can allow or deny the application to access his emails.

const string userEmailAccount = "alice@gmail.com";
const string consumerKey = "anonymous";
const string consumerSecret = "anonymous";

// First: get request token
ParameterList parameters1 = OAuth.ForUrl(
        "https://www.google.com/accounts/OAuthGetRequestToken")
    .Consumer(consumerKey, consumerSecret)
    .AddParameter("scope", "https://mail.google.com/")
    .AddParameter(OAuthParameterName.OAuthCallback, "oob")
    .Sign()
    .ExecuteWebRequest();

// Second: user interaction
string url2 = OAuth.ForUrl(
        "https://www.google.com/accounts/OAuthAuthorizeToken")
   .Consumer(consumerKey, consumerSecret)
   .Token(parameters1.GetValue(OAuthParameterName.OAuthToken))
   .TokenSecret(parameters1.GetValue(OAuthParameterName.OAuthTokenSecret))
   .Sign()
   .GetUrl();

// Fire up the browser
Process.Start(url2);
Console.WriteLine("Please enter the key: ");
string key = Console.ReadLine().Trim();

// Third: get access token
ParameterList parameters3 = OAuth.ForUrl(
        "https://www.google.com/accounts/OAuthGetAccessToken")
   .Consumer(consumerKey, consumerSecret)
   .Token(parameters1.GetValue(OAuthParameterName.OAuthToken))
   .TokenSecret(parameters1.GetValue(OAuthParameterName.OAuthTokenSecret))
   .AddParameter("oauth_verifier", key)
   .Sign()
   .ExecuteWebRequest();

// Log-in to IMAP server using XOAuth
using (Imap client = new Imap())
{
    client.ConnectSSL(TestConstants.GmailImapServer);

    string imapUrl = string.Format(
        "https://mail.google.com/mail/b/{0}/imap/", userEmailAccount);

    string oauthImapKey = OAuth.ForUrl(imapUrl)
        .Consumer(consumerKey, consumerSecret)
        .Token(parameters3.GetValue(OAuthParameterName.OAuthToken))
        .TokenSecret(parameters3.GetValue(OAuthParameterName.OAuthTokenSecret))
        .Sign()
        .GetXOAuthKey();

    client.LoginOAUTH(oauthImapKey);

    // Now you can access user's emails.

    client.Close(true);
}

However they require a specific, but non-standard IMAP command to be sent before login is done. The command is: “ID (“GUID” “1″)”

// C#
imap.SendCommand(@"ID (""GUID"" ""1"")");

' VB
imap.SendCommand("ID (""GUID"" ""1"")")

There is also an IMAP server running at imap-ssl.mail.yahoo.com; it uses SSL on the standard port 993.

Here’s the full C# version of the code:

using (Imap imap = new Imap())
{
    imap.Connect("imap.mail.yahoo.com");
    imap.SendCommand(@"ID (""GUID"" ""1"")");

	imap.Login("user", "password");

	imap.SelectInbox();
	List<long> uidList = imap.Search(Expression.All());
	foreach (long uid in uidList)
	{
		IMail email = new MailBuilder()
    			.CreateFromEml(imap.GetMessageByUID(uid));
		Console.WriteLine(email.Subject);
	}
	imap.Close(true);
}

and VB.NET version:

Using imap As New Imap()
	imap.Connect("imap.mail.yahoo.com")
	imap.SendCommand("ID (""GUID"" ""1"")")

	imap.Login("user", "password")

	imap.SelectInbox()
	Dim uidList As List(Of Long) = imap.Search(Expression.All())
	For Each uid As Long In uidList
		Dim email As IMail = New MailBuilder() _
			.CreateFromEml(imap.GetMessageByUID(uid))
		Console.WriteLine(email.Subject)
	Next
	imap.Close(True)
End Using

Differences:
- non-standard command ID command is required before any other command.
- Examine explicitly requires CLOSE command (Imap.CloseCurrentFolder), otherwise subsequent SELECT (Imap.Select) has no effect and mailbox is still in read-only state
- IDLE is not implemented.
- SELECT for not existing folder does not create new folder.

You can download the latest version of Mail.dll .NET IMAP client here

Mail.dll .NET email component has support for popular iCalendar standard.

iCalendar is used by most popular email clients like Outlook or GMail. It allows Internet users to send meeting requests and tasks to other Internet users, via email, or sharing files with an extension of .ics.

Recipients of the iCalendar data file (with supporting software, such as an email client or calendar application) can respond to the sender easily or counter propose another meeting date/time.

First make sure that your ‘usings’ or ‘Imports’ section includes all needed namespaces:

// C#

using Lesnikowski.Mail;
using Lesnikowski.Mail.Fluent;
using Lesnikowski.Mail.Appointments;

' VB.NET

Imports Lesnikowski.Mail
Imports Lesnikowski.Mail.Fluent
Imports Lesnikowski.Mail.Appointments

And now the code.

First we’ll create an appointment object add new event to it:

Appointment appointment = new Appointment();
Event e = appointment.AddEvent();

Then we need to set start and end dates:

e.Description = "Status meeting description";
e.Summary = "Status meeting summary";
e.Start = new DateTime(2010, 05, 10, 16, 00, 00);
e.End = new DateTime(2010, 05, 10, 17, 00, 00);

Now we’ll add all required and optional participants to it:

e.SetOrganizer(new Person("Alice", "alice@mail.com"));

e.AddParticipant(new Participant(
	"Bob", "bob@mail.com", ParticipationRole.Required, true));
e.AddParticipant(new Participant(
	"Tom", "tom@mail.com", ParticipationRole.Optional, true));
e.AddParticipant(new Participant(
	"Alice", "alice@mail.com", ParticipationRole.Required, true));

We’ll add an alarm to the event (set 15 minutes before the event start):

Alarm alarm = e.AddAlarm();
alarm.BeforeStart(TimeSpan.FromMinutes(15));

Finally we’ll create an email add the appointment to it and send it:

Mail.Text("Status meeting at 4PM.")
	.Subject("Status meeting")
	.From("alice@mail.com")
    .To("bob@mail.com")
    .AddAppointment(appointment)
    .UsingNewSmtp()
    .WithCredentials("alice@mail.com", "password")
	.Server("smtp.mail.com")
	.WithSSL()
	.Send();

The entire C# code looks as follows:

Appointment appointment = new Appointment();

Event e = appointment.AddEvent();
e.Description = "Status meeting description";
e.Summary = "Status meeting summary";
e.Start = new DateTime(2010, 05, 10, 16, 00, 00);
e.End = new DateTime(2010, 05, 10, 17, 00, 00);

e.SetOrganizer(new Person("Alice", "alice@mail.com"));

e.AddParticipant(new Participant(
	"Bob", "bob@mail.com", ParticipationRole.Required, true));
e.AddParticipant(new Participant(
	"Tom", "tom@mail.com", ParticipationRole.Optional, true));
e.AddParticipant(new Participant(
	"Alice", "alice@mail.com", ParticipationRole.Required, true));

Alarm alarm = e.AddAlarm();
alarm.BeforeStart(TimeSpan.FromMinutes(15));

Mail.Text("Status meeting at 4PM.")
	.Subject("Status meeting")
	.From("alice@mail.com")
    .To("bob@mail.com")
    .AddAppointment(appointment)
    .UsingNewSmtp()
    .WithCredentials("alice@mail.com", "password")
	.Server("smtp.mail.com")
	.WithSSL()
	.Send();

…and the VB.NET version:

Dim appointment As New Appointment()

Dim e As [Event] = appointment.AddEvent()
e.Description = "Status meeting description"
e.Summary = "Status meeting summary"
e.Start = New DateTime(2010, 5, 10, 16, 0, 0)
e.[End] = New DateTime(2010, 5, 10, 17, 0, 0)

e.SetOrganizer(New Person("Alice", "alice@mail.com"))

e.AddParticipant(New Participant( _
	"Bob", "bob@mail.com", ParticipationRole.Required, True))
e.AddParticipant(New Participant( _
	"Tom", "tom@mail.com", ParticipationRole.[Optional], True))
e.AddParticipant(New Participant( _
	"Alice", "alice@mail.com", ParticipationRole.Required, True))

Dim alarm As Alarm = e.AddAlarm()
alarm.BeforeStart(TimeSpan.FromMinutes(15))

Mail.Text("Status meeting at 4PM.") _
	.Subject("Status meeting") _
	.From("alice@mail.com") _
	.[To]("bob@mail.com") _
	.AddAppointment(appointment) _
	.UsingNewSmtp() _
	.WithCredentials("alice@mail.com", "password") _
	.Server("smtp.mail.com") _
	.WithSSL() _
	.Send()

You can download Mail.dll .NET email component here.

IMAP4 servers that support IDLE will include this programming string in the result of their CAPABILITY command.

You can use Capability method to check server’s capability list

// C# code

using (Imap client = new Imap())
{
	client.ConnectSSL("imap.server.com");
	client.Capability().ForEach(Console.WriteLine);
	client.Close();
}

' VB.NET code

Using client As New Imap()
	client.ConnectSSL("imap.server.com")
	client.Capability().ForEach(Console.WriteLine)
	client.Close()
End Using

Mail.dll IMAP client supports IDLE command.

There are two important methods:

• Idle() – starts accepting real-time notifications. The method hangs until a notification is received.
• StopIdle() – stops accepting real-time notifications.

// C# code

using (Imap client = new Imap())
{
    client.ConnectSSL("imap.server.com");
    client.Login("user@server.com", "password");

    FolderStatus folderStatus = client.SelectInbox();
    Console.WriteLine("Total message count: {0}",
        folderStatus.MessageCount);

    while(true)
    {
        FolderStatus currentStatus = client.Idle();
        Console.WriteLine("Total message count: {0}",
                currentStatus.MessageCount);
        foreach(long uid in client.SearchFlag(Flag.Unseen))
        {
            IMail email = new MailBuilder().CreateFromEml(
                client.GetHeadersByUID(uid));
            Console.WriteLine(email.Subject);
        }
    }
    client.Close();
}

' VB.NET code

Using client As New Imap()
	client.ConnectSSL("imap.server.com")
	client.Login("user@server.com", "password")

	Dim folderStatus As FolderStatus = client.SelectInbox()
	Console.WriteLine("Total message count: {0}",_
		folderStatus.MessageCount)

	While True
		Dim currentStatus As FolderStatus = client.Idle()
		Console.WriteLine("Total message count: {0}",_
			currentStatus.MessageCount)
		For Each uid As Long In client.SearchFlag(Flag.Unseen)
			Dim email As IMail = New MailBuilder()_
 				.CreateFromEml(client.GetHeadersByUID(uid))
			Console.WriteLine(email.Subject)
		Next
	End While
	client.Close()
End Using

Now lets handle stop gracefully:

// C# code

using (Imap client = new Imap())
{
    client.ConnectSSL("imap.server.com");
    client.Login("user@server.com", "password");

    FolderStatus folderStatus = client.SelectInbox();
    Console.WriteLine("Total message count: {0}",
        currentStatus.MessageCount);

    bool stop = false;
    // We start a new thread to handle user input, <enter> = stop idle
    new Thread(() =>
	{
		Console.ReadLine();
		client.StopIdle();
		stop = true;
	}).Start();

    while(stop == false)
    {
        FolderStatus currentStatus = client.Idle();
        if (stop == true)
            break;

        Console.WriteLine("Total message count: {0}",
            currentStatus.MessageCount);

        foreach(long uid in client.SearchFlag(Flag.Unseen))
        {
            IMail email = new MailBuilder().CreateFromEml(
                client.GetHeadersByUID(uid));
            Console.WriteLine(email.Subject);
        }
    }
    client.Close();
}

' VB.NET code

Using client As New Imap()
	client.ConnectSSL("imap.server.com")
	client.Login("user@server.com", "password")

	Dim folderStatus As FolderStatus = client.SelectInbox()
	Console.WriteLine("Total message count: {0}",_
		currentStatus.MessageCount)

	Dim [stop] As Boolean = False
	' We start a new thread to handle user input, <enter> = stop idle
	New Thread(Function() Do
		Console.ReadLine()
		client.StopIdle()
		[stop] = True
	End Function).Start()

	While [stop] = False
		Dim currentStatus As FolderStatus = client.Idle()
		If [stop] = True Then
			Exit While
		End If

		Console.WriteLine("Total message count: {0}",_
			currentStatus.MessageCount)

		For Each uid As Long In client.SearchFlag(Flag.Unseen)
			Dim email As IMail = New MailBuilder()_
				.CreateFromEml(client.GetHeadersByUID(uid))
			Console.WriteLine(email.Subject)
		Next
	End While
	client.Close()
End Using

.

Here’s why: in most folders, deleting a message simply removes that folder’s label from the message, including the label identifying the message as being in your Inbox.

[Gmail]/All Mail shows all of your messages, whether or not they have labels attached to them.

If you want to permanently delete a message from all folders:

1. Move it to the [Gmail]/Trash folder.
2. Delete it from the [Gmail]/Trash folder.

All emails in [Gmail]/Spam and [Gmail]/Trash are deleted after 30 days.
If you delete a message from [Gmail]/Spam or [Gmail]/Trash, it will be deleted permanently.

Here’s how this looks like using Mail.dll IMAP client:

// C# version:

using(Imap imap = new Imap())
{
	imap.Connect("imap.gmail.com");
	imap.Login("user", "password");

	// Find all emails we want to delete
	imap.SelectInbox();
	List<long> uids = imap.Search(
		Expression.Subject("email to delete"));

	// Delete each email permanently
	foreach (long uid in uids)
	{
		// Move to Trash
		long uidInTrash = (long)imap.MoveByUID(uid, "[Gmail]/Trash");

		// Delete from Trash
		imap.Select("[Gmail]/Trash");
		imap.DeleteMessageByUID(uidInTrash);
	}
	imap.Close(true);
}

' VB.NET version:

Using imap As New Imap()
	imap.Connect("imap.gmail.com")
	imap.Login("user@gmail.com", "password")

	' Find all emails we want to delete
	imap.SelectInbox()
	Dim uids As List(Of Long) = imap.Search(_
		Expression.Subject("email to delete"))

	' Delete each email permanently
	For Each uid As Long In uids
		' Move to Trash
		Dim uidInTrash As Long = imap.MoveByUID(uid, "[Gmail]/Trash")

		' Delete from Trash
		imap.[Select]("[Gmail]/Trash")
		imap.DeleteMessageByUID(uidInTrash)
	Next
	imap.Close(True)
End Using