The API allows you to add Watermark to all the attachments of supported types in an email message as shown in the following code sample.
advanced_usage.add_Watermarks_to_email_attachments.EmailAddWatermarkToAllAttachments
TextWatermark Watermark = new TextWatermark("Test Watermark", new Font("Arial", 19)); EmailLoadOptions loadOptions = new EmailLoadOptions(); // Specify an absolute or relative path to your document. Ex: "C:\\Docs\\message.msg" Watermarker Watermarker = new Watermarker("message.msg", loadOptions); EmailContent content = Watermarker.getContent(EmailContent.class); for (EmailAttachment attachment : content.getAttachments()) { // Check if the attached file is supported by GroupDocs....Watermark Product Solution GroupDocs...GroupDocs.Watermark Product Family / GroupDocs.Watermark for Java...