It until he touches it. People love having a tactile experience with everything they buy or at least want to get what they see on their device. The same is true for emails. A broken or misaligned email is a major drag on anyone and can force someone to stop engaging with your emails. But no one intentionally develops bad email design. So who is the culprit? Email developers who haven't tested their emails are to blame for this. Progress in the field of email development has been by leaps and bounds, but unfortunately most email clients have yet to catch up with the pace at which email development is changing. Even though css coding was introduced in html emails around 2009, most email clients still do not provide proper support for And some clients have even stepped back in the name of progress (yes, outlook… we talking about you). You must be wondering why different email clients treat the same email differently. The reason for this is the rendering engine used by the email client. The company mailing list rendering engine, in general, draws structured text from html and formats it correctly according to the styles declared in css. If the renderer does not support css style sheets or removes css, the email will look different from the original design. Mail clients on some devices use proprietary rendering engines and webmail such as gmail and yahoo mail "Piggyback" to the rendering engine used by the browser in which they are opened. Apple mail, Outlook for mac, and ios mail use the webkit safari rendering engine, which supports almost any kind of innovation you throw at it. Thunderbird uses mozilla's proprietary gecko engine to support most of the innovation elements of messaging. Microsoft outlook used internet explorer until outlook 2003, then switched to microsoft word from outlook 2007 (bad decision). According to a litmus survey, here are the shares of email clients used worldwide in june 2017. Most popular email clients by users by lirmus so even though most subscribers use apple mail (~49%), you need to make sure your emails render in gmail, outlook, and windows mail as they do on apple devices. This is especially in the case of outlook