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How to: Attach a File to an Outlook Email Message

This topic describes how to programmatically attach one or more files to an outgoing email message in Microsoft Outlook.

Provided by:  Ken Getz, MCW Technologies, LLC

In Outlook, the Attachments property of the MailItem object supports attaching one or more files to an email message. To attach one or more files to a mail item before sending the item, you call the Add(Object, Object, Object, Object) method of the Attachments object for each of the attachment files. The Add method allows you to specify the file name (the Source parameter) and the attachment type (the Type parameter) by using the OlAttachmentType enumeration. For files in the file system, specify the Type parameter as the Outlook.olAttachmentType.olByValue enumerated value.

Note Note

Since Microsoft Office Outlook 2007, you would always use this value to attach a copy of a file in the file system; Outlook.olAttachmentType.olByReference is no longer supported.

In addition, when you send an email in Rich Text Format (RTF), you can also specify two other optional parameters—Position and DisplayName—when you call the Add method. The Position parameter allows you to specify the position within the email where the attachment should appear. Use one of the following values for the Position parameter:

  • The value 0 hides the attachment within the body of the email.

  • The value 1 places the attachment before the first character.

  • A number that is larger than the number of characters in the body of the email item places the attachment at the end of the body text.

For RTF email messages, you can also specify the DisplayName parameter, which provides the name that is displayed within the body of the message for the attachment. For plain text or HTML email messages, the attachment displays only the name of the file.

The SendEmailWithAttachments sample procedure in the code example later in this topic accepts the following:

  • A reference to the Outlook Application object.

  • Strings that contain the subject and body of the message.

  • A generic list of strings that contain a list of the SMTP addresses for recipients of the message.

  • A string that contains the SMTP address of the sender.

  • A generic list of strings that contain the paths for the files to be attached.

After creating a new email item, the code adds each recipient to the Recipients collection property of the mail item. Once the code calls the ResolveAll() method, it sets the Subject and Body properties of the mail item before looping through each item in the provided list of attachment paths, adding each to the Attachments property of the mail item.

Before actually sending the email, you must specify the account from which to send the email message. One technique for finding this information is to use the SMTP address of the sender. The GetAccountForEmailAddress function accepts a string that contains the sender's SMTP email address, and returns a reference for the corresponding Account object. This method compares the sender's SMTP address with the SmtpAddress property for each configured email account defined for the session's profile. application.Session.Accounts returns an Accounts collection for the current profile, tracking information for all accounts including Exchange, IMAP, and POP3 accounts, each of which can be associated with a different delivery store. The Account object that has an associated SmtpAddress property value that matches the sender's SMTP address is the account to use to send the email message.

After identifying the appropriate account, the code completes by setting the SendUsingAccount property of the mail item to that Account object, and then calling the Send() method.

The following managed code samples are written in C# and Visual Basic. To run a .NET Framework managed code sample that needs to call into a Component Object Model (COM), you must use an interop assembly that defines and maps managed interfaces to the COM objects in the object model type library. For Outlook, you can use Microsoft Visual Studio and the Microsoft Outlook Primary Interop Assembly (PIA). Before you run managed code samples for Microsoft Outlook 2010, ensure that you have installed the Outlook 2010 PIA and have added a reference to the Microsoft Outlook 14.0 Object Library component in Visual Studio. You should use the following code samples in the ThisAddIn class of a Visual Studio Tools for Office add-in for Outlook, such that the Application object in the code is a trusted Outlook Application object provided by ThisAddIn.Globals. For more information about using the Outlook PIA to develop managed Outlook solutions, see the Outlook 2010 Primary Interop Assembly Reference on MSDN.

The following code shows how to programmatically attach files to an outgoing email message in Outlook. To demonstrate this functionality, in Microsoft Visual Studio 2010, create a new managed Outlook add-in named AttachFileAddIn, and replace the contents of the ThisAddIn.vb or ThisAddIn.cs file with the example code shown here. Modify the ThisAddIn_Startup procedure to include a reference to a file in your file system, and update the email addresses appropriately. The SMTP address included in the call to the SendMailWithAttachments procedure must correspond to the SMTP address of one of the outgoing email accounts you have previously configured in Outlook.

using System.Collections.Generic;
using Outlook = Microsoft.Office.Interop.Outlook;
namespace AttachFileAddIn
    public partial class ThisAddIn
        private void ThisAddIn_Startup(object sender, System.EventArgs e)
            List<string> attachments = new List<string>();
            List<string> recipients = new List<string>();
            SendEmailWithAttachments(Application, "Test", "Body", recipients, "", 
        private void ThisAddIn_Shutdown(object sender, System.EventArgs e)
        private void SendEmailWithAttachments(Outlook.Application application, 
            string subject, string body, List<string> recipients, 
            string smtpAddress, List<string> attachments)
            // Create a new MailItem and set the To, Subject, and Body properties.
            var newMail = application.CreateItem(Outlook.OlItemType.olMailItem) as Outlook.MailItem;
            // Set up all the recipients.
            foreach (var recipient in recipients)
            if (newMail.Recipients.ResolveAll())
                newMail.Subject = subject;
                newMail.Body = body;
                foreach (string attachment in attachments)
                    newMail.Attachments.Add(attachment, Outlook.OlAttachmentType.olByValue);
            // Retrieve the account that has the specific SMTP address.
            Outlook.Account account = GetAccountForEmailAddress(application, smtpAddress);
            // Use this account to send the e-mail.
            newMail.SendUsingAccount = account;
        private Outlook.Account GetAccountForEmailAddress(Outlook.Application application, 
            string smtpAddress)
            // Loop over the Accounts collection of the current Outlook session.
            Outlook.Accounts accounts = application.Session.Accounts;
            foreach (Outlook.Account account in accounts)
                // When the email address matches, return the account.
                if (account.SmtpAddress == smtpAddress)
                    return account;
            // If you get here, no matching account was found.
            throw new System.Exception(string.Format("No Account with SmtpAddress: {0} exists!", 
        #region VSTO generated code
        /// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        private void InternalStartup()
            this.Startup += new System.EventHandler(ThisAddIn_Startup);
            this.Shutdown += new System.EventHandler(ThisAddIn_Shutdown);