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 Fab4 responsive technique: stability and usefulness beyond Gmail

email client tricks

Responsive Emails has been a trending topic in Email Marketing since last five years. Today most emails are read on mobile devices, so responsiveness is a must, but many email clients and webmails have a really limited support of media query, the main css way to make responsive html layout.


Until Sept 2016 (when Gmail started supporting non-inline styles and media queries), the most problematic clients were Outlook and Gmail (both web and app); to overcome these problems many techniques have been developed - mainly table based layouts with conditional comments to satisfy Outlook a lot of inlined CSS to make Gmail happy.

Someone started to use mobile-first templates, letting media queries manage the desktop version - where it was possible.

Then Hybrid Coding / Spongy technique emerged: a mix of well balanced inline styles, with min-width/max-with and width tricks, letting also Gmail have its proper adaptive version even if not fully responsive.

Hybrid coding has been adopted by many email templates (also Versafix-1 Mosaico Template use it) even if the rendering of responsive version in Gmail was not perfect.

A different approach

A new technique emerged early in 2016, called the Fab4, mixing the width, min-width, max-width (all already used in hybrid coding) with a CSS calc() trick.

Fab4 has a completely different approach: no table based layout - all inline-block divs - and a calc() based breakpoint, based on the parent width instead of media queries.

Fab4 code

The basic is (to be inlined):

.block {
    width:calc((480px — 100%) * 480);

In this brief example 480px is the brackpoint: if parent width is under 480px the calc-computed .block width will be over the max-with of 100%, so the div will limit its width to the max-width value, occupying the whole space, making multiple .block stack in a single column.

If the parent width is over 480px, then the calculated width will be a negative number, so the box will shrink to the min-width of 50%, and the .block will be arranged into a two columns layout.

The method is really smart but has 2 big limits:

  • calc is not supported by all clients
  • many webmails may strip down parenthesis or the whole calc property value

For the record the final version proposed in the original article is:

.block {
    width:-webkit-calc(230400px — 48000%);
    width:calc(230400px — 48000%);

This simply introduces “-webkit-“ prefixed calc so to support older WebKits and does the math in the calc expression because some webmail removes styles with an asterisk or double brakets.

So, the method proved to be solid and Campaign Monitor has rewritten its responsive templates to use this technique - alongside a series of conditional comments table layout bit and other minor tricks to achieve complete Outlook compatibility.

But now Gmail supports media queries

So, is the Fab4 method still useful? Maybe.

If you look at global shares Gmail was the only email client having a need for the Fab4 method, but if you send to specific non-US markets or you also care for less used email clients then you may still need it.

Here is a list of local/regional providers that you don’t find in “global stats” but are big in specific countries:

  • Russia:,,
  • China:,
  • India:,
  • Germany:,,
  • France:,,,
  • Italy:,,, Tiscali
  • Brazil: Terra, Uol, Bol
  • Spain: Terra, Teleline
  • Portugal: Sapo, Telepac

For example in Italy (we are italian so we prefer to talk about what we know well) the 4 “local” providers above generate more than 30% of total email opens and alone is the first provider with more users than Gmail.

So, it worth testing each “method” also against webmails or mobile apps being relevants for your target and not only against the major global providers.

In our tests we found that, Terra, GMX, and Yandex will show Fab4 mobile version, failing to use whole desktop space, when available. On the same webmail systems, spongy technique (tested with our Versafix-1 template) works well, showing full desktop version. has problem with both tecnique, but slightly minor with Versafix-1/hybrid/spongy; on Lotus Notes 8.5 Fab4 fails in bad ways, while Versafix-1 looks good.

By now we know that Gmail transition towards full media query support is not yet completed: IOS client seems to be stuck on “old” Gmail rendering system and also Gmail webmail mobile version is not accepting media query so far. On both Gmail version (IOS and Webmail mobile) Fab4 technique works well.


As said before, Fab 4 technique is born mainly to go beyond “old” Gmail limits, and give a proper responsive email version also on non media query compatible webmail and clients.

With brand new Gmail media query support this need seems to be outdated, but so far transition is still uncomplete and there are also many local webmail that are incompatible with media query.

To sum up Fab4 could be a nice option if you are mostly mobile-oriented: this method renders slightly better in mobile versions than Spongy/Hybrid technique (not so much, by the way), anyways you have also to consider that Spongy/Hybrid technique seems to react in a more solid way with “problematic” clients and webmails.

 2016/10/21  Read More

 The Perfect Email CSS Inliner

email client tricks

In order to make emails and email templates compatible with most of the clients and webmails out there, we know that we have to avoid at most everything that is not pure inline css1 style.

To be honest this is true mainly for the two bad guys of email rendering - Outlook and Gmail - but a lot of other webmails and clients have some glitches and behaviour that makes inline style the good choice.

Coding direct inline styles is really an hell of work, and every little adjustment means tons of code, with lot of errors and mistyping.

So here come Email CSS inliners: these lovely pieces of code take your css and html and give you back your “css inlined” email template, ready to be sent.

Simple (ahem…) and effective (ahem…), but how inliners do work and how much are they reliable?

How do I choose my inliner? Many ESP have their native inliners, and some other are available on web or as library.

We tried to analize the most used of them, in order to understand the strategy behind, the weakness and the strenghts.

 2016/06/22  Read More

 About unexpected scrollbars in the Yahoo webmail

email client tricks

Every single webmail system has its way to handle email rendering: to avoid security issues and to prevent css inconsistent transformation of the whole interface, webmail systems cut and transform many css instructions. One of the most strict is Gmail: no style, no mediaquery, and many css properties being deleted.

Yahoo works in a similar way, too, but recently they changed something and @nicolemerlin tweeted:

Yahoo! Mail seems to be adding overflow-x:auto to long divs, resulting in scrollbars + content squishing/stacking

It turned out that if you use max-width and max-height inline properties, then Yahoo will add an odd “overflow-x: auto” and/or “overflow-y:auto”. The use of max-width and max-height properties, otherways, is common, if you consider that Yahoo will transform any “width” and “height” properties in “min-width” and “min-height”.

The reason the overflow properties is added is not clear, yet: maybe it could be to prevent hiding some content from the message.

 2016/06/13  Read More

 Minimum Font Size in Postbox for Mac

email client tricks

Email clients world is wide and complex: not considering the most used ones, there’s a whole bunch of “minor” clients for every device and operative system.

Every client has his bugs and glitches (and template editors like Mosaico exist to simplify all this mess), and there’s no day without a new surprise. This time we talk about Postbox for Mac, a powerful, yet not so used, client; his rendering engine is based on Gecko, like Thunderbird.

So we do not expect much suprises from this wonderful client. Mhh, not so much, but we’ve found one behavior that’s not “standard” and that potentially breaks one of the classical trick used to keep a table cell narrow as we want - with a background color.

 2016/03/30  Read More

 Outlook 2016 madness and the weird 1px thin horizontal lines

email client tricks

Skip this paragraph if you already know Outlook s**ks since 2007

You probably know Outlook 2007 introduced a new email rendering engine to Outlook, named Word. The big idea from Microsoft was to replace an html rendering engine with a wordprocessor rendering engine. This means most email out there now are full of coditional comments and the world is wasting petabytes and thousands email developers hours because of this brilliant choice. Microsoft already made a few major releases (Outlook 2010 and Outlook 2013) but still use the same rendering engine. Until Outlook 2016 the email rendering was really similar between the 3 versions, but now, with Outlook 2016 Microsoft brought this to an higher level: they keep using Word, but they introduced some more bugs to make us happy.

The issue

In the last few months I’ve started hearing people complaining because of weird 1px thick horizontal lines appearing in the middle of their email when opened in Outlook 2016.

A couple of months ago a Mosaico user reported an issue against Mosaico’s Master template, Versafix-1.

So, I decided to investigate the issue and find out the problem, but I failed

 2016/03/24  Read More

 Email clients tracking and privacy issues

email client tricks

Most email marketers use “hidden” images in order to track opens, along with openers IP and user agent, they are often called “tracking pixel” or “webbug”.

These informations are vital to email senders and can be used to geo-localize users or detect the device/client they use to read email.

Like “cookies”, email tracking has been criticized for years, and most email clients implemented solutions to block remote contents until the user willingly unblock them. Nowadays most clients, and also webmail, don’t “bore” their users with broken images and tedious unblock systems.

IOS mail app and Mac Os X “Apple Mail” have been the first to launch this “new wave”, and they also provide the best experience with regard to support for “web-level” HTML support. “Modern” HTML provides many ways to include remote content within the html body: audio, css, video and also scripts.

Some of these “features” bring not only privacy issues, but also security issues.

Most email clients have methods to get rid of most of them, but sometimes you wouldn’t expect how many privacy holes can be hidden in a simple email being viewed. Mike Cardwell developed Email Privacy Tester in order to test the behaviour of various email clients and webmail BEFORE and AFTER the image unblock, so that anyone can privacy-proof his email client.

 2016/01/20  Read More

 Outlook images: vspace, hspace, align madness

email client tricks

Once again Outlook seems to be a nightmare for all email coders. In the process of design and coding the Versafix template used in Mosaico, we faced many strange and subtle issues in the way browsers and clients render the final results. One of the worst issues at first seemed just a little glimpse in the way Outlook manage the Social Icons block. In order to let the user specify the number and the type of icons, we just manage them as simple inline IMGs, specifing an hspace properties (since we know that Outlook does not render css margin)

<img hspace="10" src="facebook.png">
<img hspace="10" src="linkedin.png">

It turned out that this solution mostly works, but Outlook 2007/10/13 do not show the “hspace”. Obviously trying to add padding/margin via CSS has no results, since Outlook merely ignore them.

 2015/12/30  Read More

 Gmail App on Android tries to shrink your email with 'munged' classes

email client tricks

Everybody knows that Gmail -web or app- does not support media query at all, stripping the whole section from emails. This for, after much try and test, retry and retest, someone figured out how to get a “simil-responsive” behaviour without css at all. This approach is called “hybrid coding” and by now is used by many template designers and also by email template builder like Mosaico. Hybrid Coding works making use of width/max-width or width/min-width couples, adding some conditional comments table structures for Outlook compatibility.

<!--[if (gte mso 9)|(lte ie 8)]>
    <table align="center" border="0" cellspacing="0" cellpadding="0" width="570">
            <td align="center" valign="top">
<div class="oldwebkit" style="max-width: 570px;">
    <table style="border-collapse: separate;border-spacing: 9px;width: 100%;max-width: 570px;background-color: #fff;" class="vb-row fullpad" bgcolor="#ffffff" border="0" cellpadding="0" cellspacing="9" width="570">
                <td class="mobile-row" style="font-size: 0;" align="center" valign="top">[...]

However this approach is not perfect: if you have three column layout, the stacked blocks on mobile version will not cover the whole screen, due to the max-width value being lower than the viewport width.

 2015/12/15  Read More