Sending tests out of RED to various clients, everything looks great. Exporting a file and uploading to various sending platforms, issues develop with <![if !mso]>. Two out of three platforms (Core Motives & Campaign Monitor) that I've tried so far don't recognize this conditional comment and either strip the condition out entirely, or strip out parts of it, mangling the code. This results in Outlook 2007-2013 not displaying properly if at all, with Outlook.com being fine.

As a test, I've replaced all <![if !mso]> comments with <!--[if !mso]> in the exported file to address clients that are not mso, and re-uploaded. All platforms recognize this syntax and conditions remain intact. However, this results in the Outlooks displaying properly except for Outlook.com. Is there a suggested work around for this?

Attached is a simple RED test file with code samples that show:
01a - the exported code straight from RED, unminified (ignore <singleline> and <unsubscribe> code, this is required for uploading to Campaign Monitor).
01b - the received code after distributed through Campaign Monitor
02a - the exported code (01a) with adjustments to <![if !mso]> (replacing it with <!--[if !mso]>)
02b - the received mso-altered code after distributed through Campaign Monitor

Also attached are some screencaps of Litmus tests (also confirmed independently with versions of Outlook 2013 & Outlook.com)

Any help would be greatly appreciated.

I just stated using RED and wonder if there's been a follow-up to your question.

FWIW, if you do nothing but save the default template and then export, the resulting code for conditional comments is, I believe, written incorrectly.

Following the steps listed above, starting at Line 1, Col 10169 the code reads

<![if !mso]><!-- --><td class="center" align="center" valign="top" style="text-align:center;"><!--<![endif]-->

Shouldn't RED be writing the opening part of the conditional statement this way to work/display correctly?

<!--[if !mso]><td class="center" align="center" valign="top" style="text-align:center;"><!--<![endif]-->

Hoping to hear that the fix is an easy one.

These conditionals were written this way because open and office exchange servers / clients do strip out the comments, causing content to appear twice.

Honestly we feel an email service provider should not strip out any code if people use their own custom HTML. Mailchimp does a great job here. We also do believe most emails do work with Campaign Monitor right now. Nevertheless, I suggest contacting them why they strip out custom code.

What we can do here is make it a setting in the next release and leave it up to you guys / the customers what to do.