Thank you for contacting Aspose support team.
This issue is tested using Aspose.Email for .NET 6.1.0 and Aspose.Words for .NET 15.12.0 but no issue is observed. You may please give try to the following sample code and let us know the feedback. Sample output is also attached here for your reference.
using (Aspose.Email.Mail.MailMessage mailMsg = Aspose.Email.Mail.MailMessage.Load(path + “Source.msg”))<o:p></o:p>
mailMsg.Save(path + "SourceByAspose.mhtml", Aspose.Email.Mail.SaveOptions.DefaultMhtml);
using (var msgStream = new MemoryStream())
var options = new Aspose.Words.LoadOptions();
options.LoadFormat = Aspose.Words.LoadFormat.Mhtml;
var document = new Aspose.Words.Document(msgStream, options);
document.Save(path + "outputByAspose.pdf", new Aspose.Words.Saving.PdfSaveOptions());