James Bell James Bell - 1 year ago 1248
Javascript Question

Use Javascript to create an HTML email in Microsoft Outlook

I'd like to create an email from a Javascript web application. I'm completely aware of the many SO questions on this (e.g. Open Outlook HTML with Chrome). There are problems with the typical answers:

  1. Mailto: link: This will let you create an email, but only in plain text (no HTML) and it does not allow for attachments.

  2. Activex: IE only, my application needs to run in Firefox and Chrome too. FF & Chrome plug-ins to allow ActiveX are security hazards and seem to be buggy.

  3. Server-side sends via SMTP: The email does not end up in the "Sent" folder for the user. Plus hurdles letting the user edit HTML in the browser and attach files.

  4. Create an Outlook .MSG file: There seem to be no libraries and little written about doing this. Apparently the file format actually has an entire FAT file storage system embedded.

Key differences between many other SO questions and mine:

  • I do have access to the client machines, so I could install
    helper applications or add-ins, change settings as needed, etc.

  • The interface does not need to actually send the mail, it only needs
    to set it up for the user.

  • I also need to be able to give the email an attachment from JS (e.g. a PDF).

I cannot be the first web app developer to face this and yet I'm unable to find a solution either commercial or open source.


I used the EML file method and it works well so far. Here's my JS code to create and trigger it:

var emlContent = "data:message/rfc822 eml;charset=utf-8,";
emlContent += 'To: '+emailTo+'\n';
emlContent += 'Subject: '+emailSubject+'\n';
emlContent += 'X-Unsent: 1'+'\n';
emlContent += 'Content-Type: text/html'+'\n';
emlContent += ''+'\n';
emlContent += htmlDocument;

var encodedUri = encodeURI(emlContent); //encode spaces etc like a url
var a = document.createElement('a'); //make a link in document
var linkText = document.createTextNode("fileLink");
a.href = encodedUri;
a.id = 'fileLink';
a.download = 'filename.eml';
a.style = "display:none;"; //hidden link
document.getElementById('fileLink').click(); //click the link

Answer Source

MSG file format is documented, but it is certainly not fun... Why not create an EML (MIME) file?

To those who want to delete or downvote this answer: the suggestion is to use the EML (MIME) format. According to the OP, he considered the MSG file format (#4), but was discouraged due to complexity or lack of JS libraries that process that format. If MSG file was considered, MIME is a much better choice - it is text based, so no special libraries are required to create it. Outlook will be able to open it just as easily as an MSG file. To make sure it is treated as an unsent message by Outlook, set the X-Unsent MIME header to 1.

UPDATE: The simplest EML file would look like the following:

To: Joe The User <joe@domain.demo>
Subject: Test EML message
X-Unsent: 1
Content-Type: text/html

Test message with <b>bold</b> text.
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