Client-specific CSS Styles

Some email clients require an extra push in order to get them to behave the way we need. For the most part, overriding those pesky default style rules is a simple proposition, requiring extra style declarations and a !important or two. There are instances where client styles can’t be overridden at all, or only with hacky work-arounds. We’ll detail here, client by client, the things you’ll need to be aware of. / Hotmail

.ExternalClass Class Override

When an email is pulled into / Hotmail, any style rules present in the email are appended with .ExternalClass. Normalizing a few of these can help create a baseline for you to work from.


.ExternalClass p,
.ExternalClass span,
.ExternalClass font,
.ExternalClass td,
.ExternalClass div{
    line-height: 100%;

<hX> Color Override / Hotmail sets its own (gross green) color on heading elements lower in level than an <h1> element. This means you need to account for headings <h2> through <h6>. Fortunately, it’s as easy as applying a !important declaration to the heading’s color property:

    color:#0066CC !important;

Outlook 2007 / 2010 / 2013

“Read in Browser” Link

It’s possible, in Outlook, to trigger the appearance of a fairly prominent “View this email in your browser” bar within the application, allowing you to drive people to view your email in a browser which will render it in a much better way than Outlook ever can.

#outlook a{

<table> Element Spacing

Outlook can sometimes add a bit of spacing on the left and right side of a <table> element that can cause some layout-related headaches. By using the vendor-specific mso-table-lspace and mso-table-rspace CSS properties, you can be rid of those spaces and continue on to tackle the million other problems caused by Outlook.


Image Resizing

Using width or height tags to resize images in your markup can create a problem in Internet Explorer browsers. If your reader is viewing an email in-browser, and that email happens to have fluid images in it, they’ll look pretty ugly as they resize. Using -ms-interpolation-mode:bicubic; ensures that your images look a little better.



WebKit Text Size Adjustment

WebKit looks for any text that happens to be sized smaller than 13px and increases it to that number, which can sometimes cause design issues in places intended for small text. Setting -webkit-text-size-adjust to none will prevent iOS platforms from resizing the text, but this method also prevents OSX applications like Safari from bumping the text size up - something that can cause issues for people who need the text size to be large. Setting -webkit-text-size-adjust to 100% seems to be the best of both worlds.


Phone Number, Address, & Date Link Colors

When iOS detects a phone number, address, or calendar date, it oh-so-helpfully sets those items as links to make it easier to immediately call, map, or add an appointment within other apps. The trouble is the that link colors are the standard ‘internet blue’, or #0000FF. This color can be difficult to read on dark backgrounds, to say nothing of it not matching the style of your email’s design. Thankfully, there’s a workaround.

First, for the phone number. In the <head> of your email, add this iOS-specific <meta> tag:

<meta name="format-detection" content="telephone=no">

Using that, iOS will no longer auto-detect and style phone numbers (Apple also lists its other tags here). You should, however, provide your own way to call from an email. You can do that by wrapping a phone number in a line and setting the href attribute with a tel value:

<a href="tel:1-800-555-5555">1-808-555-5555</a>

You can now style the link as you see fit. Addresses and dates work a little differently, and the solution is a little hacky, but that’s okay; it’s par for the course in HTML email. In order to override the blue link color, you wrap the links in an inline element like an <a>, then you apply your own color:

Visit EmailCo. at <a href="#" style="color:#000000; text-decoration:none;">123 Atlantic Ave. &bull; Atlanta, GA 30318 USA</a>

Be aware that, regardless of the fact that you changed the link colors, the iOS functionality isn’t disabled on any of these items. An errant tap of a date or address will still open up calendar and map applications, so it’s a good idea to make these links a little different than your other standard links, so folks avoid confusion or frustration.

Windows Mobile

Windows Mobile Text Size Adjustment

Much like in OSX and iOS, small text is also resized on Windows Mobile. The same vendor-prefix-based CSS property is used here, just with the ms vendor prefix instead of the webkit one.