Download email attachments in .NET

.NET framework does not contain classes that allow access to email servers (SmtpClient can only send messages). Having this in mind, the first thing you’ll need is an .NET IMAP component or .NET POP3 component to download emails from the server.

IMAP and POP3 are protocols that allow communication with email servers, like Exchange or Gmail, and download email messages. IMAP is more robust, as it allows searching and grouping emails into folders. You can see IMAP vs POP3 comparision here.

The email attachments are downloaded along with the email message. Attachments are stored within the email as part of a mime tree. Usually Quoted-Printable or Base64 encoding is used. This is why apart of an IMAP/POP3 client, MIME parser is needed. Mail.dll is going to parse such MIME tree for you and expose all attachments as well-known .NET collections. Of course all other email properties, like subject, date, recipients and body, are also available.

IMail (class that represents an email after it was downloaded and parsed) uses 4 collections for storing attachments:

  • IMail.Attachments – all attachments (includes Visuals, NonVisuals and Alternatives).
  • IMail.Visuals – visual elements, files that should be displayed to the user, such as images embedded in an HTML email.
  • IMail.NonVisuals – non visual elements, “real” attachments.
  • IMail.Alternatives – alternative content representations, for example ical appointment.

Below you’ll find samples of how you can save all attachments to disk using C# and VB.NET via POP3 and IMAP protocols.

Download attachments from IMAP server

// C#

using(Imap imap = new Imap())
{
	imap.Connect("imap.example.com");   // or ConnectSSL for SSL
	imap.UseBestLogin("user", "password");

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

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

		Console.WriteLine(email.Subject);

		// save all attachments to disk
		foreach(MimeData mime in email.Attachments)
		{
			mime.Save(mime.SafeFileName);
		}
	}
	imap.Close();
}
' VB.NET

Using imap As New Imap()
	imap.Connect("imap.example.com")   ' or ConnectSSL for SSL
	imap.UseBestLogin("user", "password")

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

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

		Console.WriteLine(email.Subject)

		' save all attachments to disk
		For Each mime As MimeData In email.Attachments
			mime.Save(mime.SafeFileName)
		Next
	Next
	imap.Close()
End Using

Download attachments from POP3 server

// C# 

using(Pop3 pop3 = new Pop3())
{
	pop3.Connect("pop3.example.com");   // or ConnectSSL
	pop3.UseBestLogin("user", "password");

	foreach (string uid in pop3.GetAll())
	{
		IMail email = new MailBuilder()
			.CreateFromEml(pop3.GetMessageByUID(uid));

		Console.WriteLine(email.Subject);

		// save all attachments to disk
		foreach(MimeData mime in email.Attachments)
		{
			mime.Save(mime.SafeFileName);
		}
	}
	pop3.Close();
}
' VB.NET

Using pop3 As New Pop3()
	pop3.Connect("pop3.example.com") ' or ConnectSSL
	pop3.UseBestLogin("user", "password")

	For Each uid As String In pop3.GetAll()
		Dim email As IMail = New MailBuilder() _
      			.CreateFromEml(pop3.GetMessageByUID(uid))

		Console.WriteLine(email.Subject)

		' save all attachments to disk
		For Each mime As MimeData In email.Attachments
			mime.Save(mime.SafeFileName)
		Next
	Next
	pop3.Close()
End Using

Accessing attachment’s data

You can also save attachment to stream (using MimeData.Save(Stream stream) method), get direct access to attachments data as stream (using MemoryStream MimeData.GetMemoryStream() method) or even as a byte array (using byte[] MimeData.Data).

Process emails embedded as attachments

In many situations you’ll receive a message that has another message attached to it. You can use Mail.dll to extract all attachments from all inner messages no matter on how deep the embedding level is.

Tags: , , , , ,

36 Responses to “Download email attachments in .NET”

  1. Vincentius Owen Says:

    Is it possible for me to delete specified email with this component?

    Thank You

  2. Limilabs support Says:

    @Vincentius Yes, you can. Both IMAP and POP3 clients have two methods: DeleteMessage and DeleteMessageByUID.

    If you are using Gmail you may want to also check this post:
    http://www.limilabs.com/blog/delete-email-permanently-in-gmail

  3. Franz Says:

    When i try the “when using pop3 sever” for C# and i keep getting the System.UnauthorizedAccessException was unhandled error. Any fixes?

  4. Limilabs support Says:

    @Franz
    1. Are you using the latest version?
    2. What is the stack trace of the exception?
    3. Please contact us via email:
    http://www.limilabs.com/support
    it’ll be much easier to help you.

  5. madhan Says:

    email.Attachments.ForEach(mime => mime.Save(mime.SafeFileName));

    “=>” showing error

  6. Limilabs support Says:

    @madhan

    Lambda expressions are supported in C# compiler 3.0 or greater .

    You can use regular foreach loop to iterate over Attachments collection.

  7. Sunil Says:

    Hi,

    Where I can change folder path for download attachments from POP3?
    What is default path?
    It’s working but i can’t able to see the download attachemnts
    Please replay

  8. Limilabs support Says:

    @Sunil
    Attachments are part of the email you download, files are not created on disk until you call MimeData.Save method on objects in Attachments collection.

    If you want to specify different folder than the default path for current process, just specify it as an argument for the Save method:

    mime.Save(@”c:\attachments\” + mime.SafeFileName)

  9. Chintan Says:

    Hi,

    I want to download .csv format file and save it to database.

    so how can i do it ???

    I dont want to save the csv format file in any harddrive.

    Please Reply.

  10. Limilabs support Says:

    @Chintan

    If the csv file is attached to the email you can directly access attachment’s data as stream using MimeData.GetMemoryStream() method:

    MemoryStream stream = mime.GetMemoryStream();
    

    or as byte array using MimeData.Data property:

    byte[] data = mime.Data;
    

    If your csv attachment has correct mime type, you can also cast MimeData to MimeText and use Text property to access csv data as string:

    string text = ((MimeText)mime).Text;
    

    As for your question on how to save this data to database, it depends on the db you are using (MSSQL, Oracle, MySql, document db) and it’s structure. I don’t think I can help you with so little information you provided and also I believe it’s out of scope of Mail.dll.

  11. Binis Says:

    How can I check if the password that a user has entered matches to its username (basically if it is correct)…..

    Thanks,
    Binis

  12. Limilabs support Says:

    @Binis Server does that.
    If the password is incorrect you’ll get an exception from Login method.

  13. Kent Says:

    What if there are multiple files in the emails, I cannot figure out how to save them all?

    Thanks,
    Kent

  14. Limilabs support Says:

    @Kent

    You should iterate over Attachments collection as shown in the blog post,
    you can use foreach loop if you are not familiar with lambdas:

    foreach (MimeData attachment in email.Attachments)
    {
        attachment.Save("c:\" + attachment.SafeFileName);
    }
    
  15. mojtaba Says:

    files don’t save completely, size of downloaded files is zero.

  16. Limilabs support Says:

    @mojtaba

    This is very unlikely as Mail.dll is rock solid product. In most cases corrupted messages are the problem. If you believe we can improve Mail.dll parser, please check the “I have problems parsing the message” article and contact us directly with the message in question.

  17. Veincorp Says:

    I purchased your mail.dll, it’s awsome, But Why downloaded visual image saved in .DAT extension, is there any way to save it in proper extension

  18. Limilabs support Says:

    @Veincorp

    Most likely the sender of the message have not specified the filename at all.
    In such case SafeFileName property (which you probably use with Save method) generates unique filename.

    You can of course check FileName property for null and act according to your needs.

  19. Lax Says:

    I have set up a IMAP gmail account
    I am trying to connect with the code :

    using (Imap imap = new Imap())
    {
    imap.Connect(“smtp.gmail.com”);
    imap.UseBestLogin(“imap.dmtrigger@gmail.com”, “password”);
    imap.SelectInbox();
    ….
    ….

    But I get this error :
    “A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond …. ”

    Would this be the problem with the account ? But I can send and recieve mails from the account I have set up in my Outlook.
    Can anyone help?

    Thanks,
    Lax.

  20. Limilabs support Says:

    @Lax,

    1. When using IMAP protocol use IMAP server: imap.gmail.com
    2. Use SSL

    using (Imap client = new Imap())
    {
        client.ConnectSSL("imap.gmail.com");
        client.Login("user@gmail.com", "password");
        client.SelectInbox();
    
        // ...
    
        client.Close();
    }
    
    
    
  21. Rajkumar Says:

    Error 1 The type or namespace name ‘Imap’ could not be found (are you missing a using directive or an assembly reference?)

  22. Limilabs support Says:

    @Rajkumar

    You need to download and add a reference to Mail.dll IMAP library:
    http://www.limilabs.com/mail/download

  23. Archana Says:

    Hi,

    Your dll is great, but there is a problem that I am facing.
    I have added the save attachment option on a button click event:


    pop3.ConnectSSL("pop.gmail.com");
    pop3.UseBestLogin("username", "password");

    IMail email = new MailBuilder().CreateFromEml(
    pop3.GetMessageByUID(lst.SelectedValue));

    foreach (MimeData attachment in email.Attachments)
    {
    if (attachment.FileName == lblAttachment.Text)
    {
    attachment.Save("c:\\" + attachment.SafeFileName);
    }
    }
    pop3.Close();

    but I get a error message that the UID does not exists, and also how do I access the sent mails (sent items)

  24. Limilabs support Says:

    @Archana,

    > I get a error message that the UID does not exists
    Most likely you are trying to download this message for a second time.
    Gmail’s POP3 behavior is quite different from other POP3 servers (http://www.limilabs.com/blog/gmail-pop3-behavior)
    I strongly advise you to use IMAP, it’s going to by much easier for you and you’ll be able to access other folders.

    To access different folder than Inbox you need to use IMAP protocol:
    http://www.limilabs.com/blog/folder-access-with-imap

  25. Archana Says:

    Thanks,
    I have another question, how to get a preview of the attachments in a selected email

  26. Limilabs support Says:

    @Archana

    I’m not sure Mail.dll can help you with that. What does “preview of the attachments” mean?

  27. Bafana Says:

    I’m getting this error”An attempt was made to access a socket in a way forbidden by its access permissions 173.194.66.108:110″ any idea?

  28. Limilabs support Says:

    @Bafana

    Mail.dll needs to establish connection to the server, it seems that your antivirus software or firewall is preventing this.
    Make sure you have antivirus/firewall software disabled or configured correctly.

  29. Jarek Says:

    Is there a way to skip attachments that are in the signature/footer of the mail (e.g. company logo etc.)?

  30. Limilabs support Says:

    @Jarek,

    As you probably know there are 3 attachment collections:

    IMail.Visuals – contains files that should be displayed to the user (usually images embedded inside HTML emails).
    IMail.NonVisuals – “real” attachments.
    IMail.Attachments – contains all attachments (this includes Visuals and NonVisuals).

    Company logo image in the footer is indistinguishable from any other images that are embedded inside HTML, so the answer to your question is no, it is not possible. But it is also not a “real” attachment (rather a visual element) – consider using IMail.NonVisuals collection.

  31. Yuvraj Says:

    Hello,

    I am using your trail application to download GMail Attachments, can you please support me for following questions:
    1. can we filter mail attachments by name & how ?
    2. can we download PDF attachments ?
    3. I want to download day wise attachments

    I want to use this in my application. So please support me for test it.

    Many Thanks !!!

  32. Limilabs support Says:

    @Yuvraj,

    > 1. can we filter mail attachments by name & how ?
    Use MimeData.FileName or MimeData.SafeFileName properties. You can find samples in this article.

    > 2. can we download PDF attachments ?
    Yes, you can download any kind of attachment.

    > 3. I want to download day wise attachments
    You can filter emails that arrived since you last check or search for messages within certain dates. You can also use Gmail’s search syntax.

    In most scenarios you download attachments along with the email message. You can however get email information and structure first and then download parts of such message.

  33. Yuvraj Says:

    That’s great Sir.

    Thanks again.
    Some more questions:
    – How i can download datewise attachments only ?
    – How to clear my Gmail session?
    – Can i stop attachment downloading in between with clearing my gmail session ?

  34. Limilabs support Says:

    @Yuvraj

    I think you should contact our support with such detailed questions.

    > How i can download datewise attachments only ?
    You can’t. IMAP server manages messages, not attachments.

    First you’ll need to search for email messages using your required criteria. Of course you can find messages within specified dates. Then you can download them entirely (see this article) -or- download message attachments only.

    > How to clear my Gmail session?
    > Can i stop attachment downloading in between with clearing my gmail session?
    I’m sorry, but I don’t understand what you try to accomplish. What do you mean by “Gmail session”? Please contact our support.

  35. Rashmi Ranjan Says:

    This is a great Mail dll for .Net

    I want to get the attachments for a selected email by passing the messageid or the uid as a parameter.

    Kindly let me know how can i do this.

  36. Limilabs support Says:

    @Rashmi Ranjan

    You can find all required code in this blog post. Use Imap.GetMessageByUID to download email message and MailBuilder.CreateFromEml to parse it. Then use IMail.Attchments collection.

Questions?

Consider using our Q&A forum for asking any questions.