Add Text Watermark to EML via C#

Build your own .NET apps to watermark EML files using server-side APIs.

How to Watermark EML File Using C#

In order to watermark EML file, we’ll use

Aspose.Email for .NET

API which is a feature-rich, powerful and easy to use document manipulation API for C# platform. Open

NuGet

package manager, search for Aspose.Email and install. You may also use the following command from the Package Manager Console.

Command
PM> Install-Package Aspose.Email

Steps to Add Watermark to EML via C#

You need the

aspose.email.dll

to try the following workflow in your own environment.

Load the HTML body of email message file
Load attachment and set its content
Set body content, if any
Save email file on disc

System Requirements

Aspose.Email for .NET is supported on all major operating systems. Just make sure that you have the following prerequisites.

Microsoft Windows or a compatible OS with .NET Framework, .NET Core, and Xamarin Platforms.
Development environment like Microsoft Visual Studio.
Aspose.Email for .NET referenced in your project.

Add Watermark to EML - C#
mail.Attachments.Add("watermark", imageBytes);

var html = mail.BodyHtml;
var htmlDocument = new Aspose.Html.HTMLDocument(mail.BodyHtml, "");

var attachment = mail.Attachments.Find(x => x.LongFileName == "watermark");
attachment.SetContentId("watermark");

var bodyHtml = htmlDocument.Body.InnerHTML;

var watermarkHtml = $@"watermarkHtml";

htmlDocument.Body.InnerHTML = watermarkHtml;

var folderPath = Path.Combine(Config.Configuration.OutputDirectory, Guid.NewGuid().ToString());
var filePath = Path.Combine(folderPath, "Merged.html");

htmlDocument.Save(filePath);

var content = System.IO.File.ReadAllText(filePath);

Directory.Delete(folderPath, true);

mail.SetBodyContent(content, BodyContentType.Html);  

About Aspose.Email for .NET API

Aspose.Email is a Microsoft Outlook and Thunderbird formats parsing solution. One can easily create, manipulate, convert email and storage formats such as MSG, EMLX, EML and MHT. Handling of email attachments, customization of message headers and implementation of different network protocols like POP3, IMAP & SMTP to send & receive emails is much easier. Its a standalone API and does not require Microsoft Outlook or any other software installation.

Watermark EML via Online App

EML What is EML File Format

EML file format represents email messages saved using Outlook and other relevant applications. Almost all emailing clients support this file format for its compliance with RFC-822 Internet Message Format Standard. Microsoft Outlook is the default software for opening EML message types. EML files can be used for saving to disc as well as sending out to recipients using communication protocols.

Other Supported Watermarking Formats

Using C#, one can easily watermark different formats including.

MSG (Outlook & Exchange Format)