Receive unseen emails using IMAP

This article describes how to receive unseen email messages using Mail.dll .net email library and IMAP protocol.

As a prerequisite you need to add reference to Mail.dll to your project. Please check MSDN how to add reference article for details.

When your reference is added you need to import correct namespaces:

// C#

using Limilabs.Mail;
using Limilabs.Client.IMAP;

' VB

Imports Limilabs.Mail
Imports Limilabs.Client.IMAP

First thing you need to do is to connect to your IMAP server.

Use Connect(string host) method to connect to the server. Typically IMAP server is working on port 143. You can use Connect(string host, int port) overload when you need to specify different port, or ConnectSSL methods to use IMAP over TLS/SSL.

// C#

using (Imap imap = new Imap ())
{
    imap.ConnectSSL("imap.example.com");  // or Connect for no SSL
    imap.UseBestLogin("user", "password");

' VB

Using imap As New Imap ()
    imap.ConnectSSL("imap.example.com")  ' or Connect for no SSL
    imap.UseBestLogin("user", "password")

Mail.dll supports OAuth 2.0 for authentication, you can find OAuth2 samples for Office365 and Gmail on the Mail.dll samples page.

For Gmail you may want to use Gmail’s App Passwords.

Next step is to select folder, download unique ids (uids) of unseen messages, and iterate through them. In this example we select Inbox, but you can use Select method to select different folder.

// C#

imap.SelectInbox();

List<long> uids = imap.Search(Flag.Unseen);
foreach (long uid in uids)

' VB

imap.SelectInbox()

Dim uids As List(Of Long) = imap.Search(Flag.Unseen)
For Each uid As Long In uids

Finally we’ll use GetMessageByUID method to download the message from the server and MailBuilder class to parse email and extract attachments:

// C#

var eml = imap.GetMessageByUID(uid)
IMail email = new MailBuilder().CreateFromEml(eml);

string subject = email.Subject;
string plainText = email.Text;

' VB

Dim eml = imap.GetMessageByUID(uid)
Dim email As IMail = builder.CreateFromEml(eml)

Console.WriteLine(email.Subject)
Console.WriteLine(email.Text)

At that point you can also access and proceses email attachments.

Here are the full samples showing how to receive e-mail messages in C# and VB.NET:

// C#

using Limilabs.Mail;
using Limilabs.Client.IMAP;

class Program
{
    static void Main(string[] args)
    {
        using(Imap imap = new Imap())
        {
            imap.ConnectSSL("imap.example.com"); // or Connect
            imap.UseBestLogin("user", "password");

            imap.SelectInbox();
            List<long> uids = imap.Search(Flag.Unseen);

            foreach (long uid in uids)
            {
                var eml = imap.GetMessageByUID(uid);
                IMail email = new MailBuilder()
                    .CreateFromEml(eml);

                string subject = email.Subject;
                string plainText = email.Text;
            }
            imap.Close();
        }
    }
};

' VB.NET

Imports Limilabs.Mail
Imports Limilabs.Client.IMAP

Public Module Module1
    Public Sub Main(ByVal args As String())
        Using imap As New Imap()
            imap.ConnectSSL("imap.example.com") ' or Connect
            imap.UseBestLogin("user", "password")

            imap.SelectInbox()
            Dim uids As List(Of Long) = imap.Search(Flag.Unseen)

            For Each uid As Long In uids
                Dim eml = imap.GetMessageByUID(uid)
                Dim email As IMail = New MailBuilder() _
                    .CreateFromEml(eml)

                Console.WriteLine(email.Subject)
                Console.WriteLine(email.Text)
            Next
            imap.Close()
        End Using
    End Sub
End Module

Just give Mail.dll a try and download it at: Mail.dll .NET email component

Get Mail.dll

Tags: C# IMAP IMAP component VB.NET

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Chris Blaisdell Says:
June 22nd, 2016 at 17:45

How do I mark them as seen after I receive them?

Limilabs support Says:
June 22nd, 2016 at 18:26

@Chris,

If you are using GetMessageByUID to download email message, most IMAP servers will automatically mark such message as seen.

You can check this article for details: mark emails as seen.

Ajay Says:
November 29th, 2016 at 07:07

Hi,

When I get all emails with Uid larger than last sync, How can I find out if particular mail is seen or unseen (read or unread)? I do not want to get the mails using Flag.Unseen as I need to sync all the mails to the client read or unread (user might have seen the mail on other client, in that case I need to show that mail as read/seen on my client)

Thanks for your help.

Limilabs support Says:
November 29th, 2016 at 08:28

@Ajay,

There are several way to achieve it:

1.
You can make a second search for unseen emails:

List<long> unseenUIds = imap.Search(Flag.Unseen);

Searches are efficient, as they only download uids. Especially unseen search, as most users only have several unseen messages.

2.
You can use GetMessageInfoByUID method that takes uid list as a parameter:
http://www.limilabs.com/blog/get-email-information-from-imap-fast
Resulting list contains many email information (subject, attachments count and names, date, from, to headers) and flags for each email. Unseen messages should contain Flag.Unseen flag in MessageInfo.Flags.Flags collection.

Ajay Says:
November 29th, 2016 at 10:41

For option 1, Can I combine the search criteria, like flag.Unseen and Uid greater than last sync?

Thanks.

Limilabs support Says:
November 29th, 2016 at 15:45

Of course, use Expression.And:

var query = Expression.And(
        Expression.UID(Range.From(largestUID + 1)),
        Expression.HasFlag(Flag.Unseen)
    );
List<long> uids = imap.Search(query);

More info on searching IMAP here.

Still searching for unseen messages should be very fast, even without the UID range part.

Puneet Says:
June 4th, 2017 at 07:31

I tried to use this but I am getting exception i.e. Unable to read data from the transport connection: An existing connection was forcibly closed by the host..

Please provide your inputs

Limilabs support Says:
June 4th, 2017 at 09:03

@Puneet,

Please disable your firewall and antivirus software. Are you sure you’ve provided all connection settings correctly? At which line did it happen? Consider reading this article if you have problems connecting.

Puneet Says:
June 4th, 2017 at 11:00

I have a requirement to read incoming email subject, body and attachment. There may multiple email addresses which I have to read using single application. Till now what I discovered from your site this can be acheived using different configurations. Requesting to confirm whether my understanding is correct?

Limilabs support Says:
June 4th, 2017 at 15:14

I’m not sure what “configurations” are you talking about, but if you have multiple accounts to check, you’ll need to connect and login to IMAP server for each of them separately.

Puneet Says:
June 5th, 2017 at 05:20

As a part of requirement I have multiple email addresses and I have to write any application to read the emails from these email addresses.
I should login with 1st email address then read and loggoff. Re-login with second email address and repeat same steps. Am I correct?

Limilabs support Says:
June 5th, 2017 at 09:27

You should connect, login, read emails and disconnect (IMAP does not have log off command). Repeat those steps if needed.

vescan Says:
November 14th, 2017 at 06:41

Is there anyway to retrieve all emails from a certain IMAP folder using one select and not one by one using GetMessageByUID. i dont know why, but for me getting emails one by one is very slow (2 emails per second)
TIA

Limilabs support Says:
November 15th, 2017 at 05:11

@vescan,

You can try getting only most important email data without downloading actual emails.

Receive unseen emails using IMAP

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