I've been using MJML.io to develop Mobile Responsive emails. MJML uses the font-size:0px "hack" to fix inline-block problems in some clients. I've recently come across an ESP that says I shouldn't use font-size:0px since it will trigger the email as SPAM. This means I have to come up with a less effective way of creating responsive emails.

Can I ignore them? or (better yet) can I get an concensus from the HTML Email community that using font-size:0px is NOT an issue and is ok to use?

Please advise. Thanks,