Prevent Outlook 365 from Removing Recipients in Programmatically Built Emails

Preventing Outlook 365 from Removing Recipients in Programmatically Built Emails

In the process of building email messages programmatically, developers often encounter an issue with Microsoft Outlook 365 removing the recipients from the email msg file upon saving. This article provides a detailed explanation of the issue, key concepts, and solutions to prevent Outlook 365 from removing recipients in programmatically built emails.

Context and Issue

When working with programmatically built email messages in C# or other programming languages, developers often save these messages as .msg files for distribution or further processing. However, Microsoft Outlook 365 has a known issue where it removes the recipients from the email when opened or manually saved, even though the recipients are present in the original .msg file.

Key Concepts

To address this issue, it is essential to understand the following key concepts:

• OOM (Outlook Object Model): The Outlook Object Model is a set of objects and interfaces for automating Microsoft Outlook tasks programmatically.
• Redemption Library: Redemption is a third-party library that simplifies interaction with the Outlook Object Model, especially when dealing with Extended MAPI, an underlying messaging architecture in Outlook.
• Extended MAPI: Extended MAPI is a set of interfaces for directly manipulating Microsoft Messaging API (MAPI) services, allowing lower-level access to Outlook data storage and functionalities.

Solution using OOM

With OOM, you can programmatically set the recipient and other email properties. However, the challenge is maintaining the recipient information when the user opens or manually saves the email in Outlook 365.

using Outlook = Microsoft.Office.Interop.Outlook;

...

// Create a new mail item
Outlook.MailItem mailItem = (Outlook.MailItem)Application.CreateItem(OlItemType.olMailItem);

// Set recipient, subject, and body
mailItem.To = "[email protected]";
mailItem.Subject = "Test Email";
mailItem.HTMLBody = "Test email body.";

// Save as msg file
string filePath = @"C:\temp\test_email.msg";
mailItem.SaveAs(filePath, OlSaveAsType.olMSG);

This solution does not prevent Outlook 365 from removing recipients when opening or manually saving the email. The workaround is to save the recipients' information in the email's body and then parse that information to restore the recipients after Outlook 365 removes them.

Solution using Redemption Library

The Redemption Library provides a more efficient solution for handling programmatically built emails and recipients. By using the Redemption SafeMailItem instead of Outlook's MailItem, you can maintain recipient information even after opening or manually saving the email in Outlook 365:

using Redemption;

...

// Create a new SafeMailItem
RDOSession session = new RDOSession();
session.Logon();
RDOFolder folder = session.GetDefaultFolder(rdoDefaultFolders.olFolderInbox);
RDOMail SafeMailItem = folder.Items.Add("IPM.Note");

// Set recipient, subject, and body
SafeMailItem.Recipients.Add("[email protected]");
SafeMailItem.Subject = "Test Email";
SafeMailItem.HTMLBody = "Test email body.";

// Save as msg file
string filePath = @"C:\temp\test_email.msg";
SafeMailItem.Save();
SafeMailItem.SaveAs(filePath, rdoSaveAsType.olMSG_ RICH_TEXT);

When dealing with programmatically built emails and Microsoft Outlook 365, you may face issues with recipients being removed upon opening or manually saving the email. This article explained the context and issue in detail, offered key concepts, and discussed the following solutions:

• Using OOM to save the recipients' information in the email's body.
• Utilizing the Redemption Library's SafeMailItem to maintain recipient information while saving the email.

References

• Type: Books
  Title: "Outlook Object Model and VBA"
  Author: Chris MacDonald
• Type: Articles
  Title: "Interop.Outlook - Save email with attachment and recipient programmatically"
  Link: https://stackoverflow.com/questions/24683529/interop-outlook-save-email-with-attachment-and-recipient-programmatically
• Type: Online resources
  Title: Redemption Library
  Link: https://www.dimastr.com/redemption/