I've had a rough time with a very small number of recipients reporting an issue with my CSS rendering as text in the body of the email.

The email passes all my Litmus tests and the only people who can reliably replicate the problem are clients so it's a difficult one to troubleshoot.

Has anyone else seen this? Luckily the client helped me debug a bit and he sent me the rendered source of the email. It shows that the <style> element included in the <head> of my email template's HTML is converted (by Outlook's Word rendering engine...) to <style_1 a,.footer-links=""> and then the rest of my CSS follows. Obviously there's no such thing as a <style_1> element so it breaks.

I've seen in some templates that all CSS placed in the <head> can be contained in an <!--[if !mso]> tag.

Will that solve the issue?

Unfortunately, as I can't replicate it myself, and the only one who can is a client, I'm hoping to understand what's going on if anyone else has seen this without bothering my client again..

Thanks in advance.