text/plain version of multipart email sent with mailkit not being received correctly

Question

I am using mimekit and mailkit to build a multi part email that contains an html body and a plain text body. The html version works fine. The plain text works fine but only when the html is not included.

When I build a multi part email that contains both text and html bodies it seems like only the html is received on both outlook and gmail. If I set my mail to only plain-text then I get text parsed out of the html body. I have looked at the original in gmail and decoded it to find it is the parsed html not the separate plain text version I am trying to send with mailkit.

Here is the code that is building and sending the email.

public void SendEmail(List toAddresses, string fromAddress, string subject, string htmlBody, string textBody)
{
        var message = new MimeMessage();

        message.From.Add(new MailboxAddress(fromAddress));

        foreach (var to in toAddresses)
        {
            message.To.Add(new MailboxAddress(to));
        }

        message.Subject = subject;

        var bodyBuilder = new BodyBuilder
        {
            HtmlBody = htmlBody,
            TextBody = textBody
        };

        message.Body = bodyBuilder.ToMessageBody();

        _smtpClient.Connect(_settings.SmtpHostServer, _settings.SmtpPortNumber);
        _smtpClient.Authenticate(_settings.SmtpUserName, _settings.SmtpUserPassword);
        _smtpClient.Send(message);
        _smtpClient.Disconnect(true);
}

When I write the message to a file it is in mime format, and has separate sections for html and plain text with the content I expect for each section.

From: ************
Date: Mon, 23 Sep 2019 09:10:35 -0600
Subject: Welcome To ************
Message-Id: 
To: ************
MIME-Version: 1.0
Content-Type: multipart/alternative; boundary="=-YWTR3eTYkSy366wQ3CLhlw=="

--=-YWTR3eTYkSy366wQ3CLhlw==
Content-Type: text/plain; charset=utf-8

=================================================================================
Welcome to ************
=================================================================================

You are receiving this email because you have registered with *****.

Please copy the following URL below into your web browser to login to *******.

https://************/login

Sincerely,

The ******* Team

=================================================================================
******** Contact Information
=================================================================================

Email: ************
Phone: ***********

--=-YWTR3eTYkSy366wQ3CLhlw==
Content-Type: text/html; charset=utf-8
Content-Id: <6MLWHEHRM8U4.ZO5T7EVTEFZ42@localhost.localdomain>




    
    
    
    
    


    
        
        
            
                
                
                    
                             
                             
                        
                    
                
                
            
        
        
        
            
                
                
                    
                        
                            Welcome to ********
                        
                    
                
                
            
        
        
        
            
                
                
                    
                    
                        


    You are receiving this email because you have registered with *********.




    
        
            
                
                    
                        
                            Login To *********
                        
                    
                
            
        
    


Sincerely,
The ******** Team
                        
                    
                
                
            
        
        
        
            
                
                
                    
                    
                        
                            
                                **********
                            
                            
                                (866) 571-5014
                            
                        
                    
                
                
            
        
    


--=-YWTR3eTYkSy366wQ3CLhlw==--

text/plain version of multipart email sent with mailkit not being received correctly

Answers (1)

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