Mobile considerations

Tips & standards for mobile, JavaScript, Flash and more

If you're building a mailing from scratch using your own HTML, we want to make sure it's optimized for all email inboxes – and for a mobile environment. We've pulled together a set of mobile-specific tips and a few other important reminders.

Here we'll cover:


Your email should be no wider than 600 pixels. Keeping your mailing 600 pixels wide (or less) ensures that it will display properly on all email clients, including mobile devices. The iPhone has a preview pane of 320px wide, Blackberry devices are around 360px and Droid is at 480px. This means most mobile device users are familiar with scrolling horizontally; however, an email wider than 600 pixels may not fit on one plane and may not display as intended.

Image sizes

Stick to reasonable image sizes. You'll want to make sure that your images fit within the dimensions of your stationery. We recommend images that are 480 x 480 pixels or smaller.

Your email's plaintext version

Give attention to your plaintext, found by switching the view of your mailing in the top right corner to plaintext instead of HTML. Unlike previous versions of Blackberry, 2011 Blackberry smartphones have been built on Apple's Webkit rendering engine and will display HTML relatively consistently across the different models, but older versions of the Blackberry (and Palm phones) will only display plaintext.


With the large number of email clients, browsers, security settings and personal settings, it's hard to know how JavaScript will be received in any given email environment. Not only can JavaScript cause browser problems for the recipient, but in many cases, it will be stripped out of the email entirely. Also, keep in mind that this application uses JavaScript, so including it in your HTML mailing may create conflicts when you upload your code. JavaScript is starting to be supported by Hotmail, but it is still too early to consider using it in your mailings, unless you're sending uniquely to Hotmail users.


Using Flash in your email design can affect both delivery and display. Spam filters are particularly hard on Flash and regularly block emails that contain it. If your email does get past the spam filter, you may still run into problems. Most email clients will strip out Flash, leaving your recipient with a blank screen. If animation is important to you, try inserting an animated GIF instead.

Streaming media

As streaming media requires an open connection to an external source, many email clients and associated firewalls will either block the email or disable the streaming media prior to it arriving in an inbox. To communicate this way, we recommend embedding a static image in your design that links to a webpage with the hosted media.

Embedded sound and movie files

Some servers will block emails with embedded video and sound files, or they'll strip out the embedded content, leaving your recipient with nothing to view or hear. Rather than embedding the media file, take a screenshot of the video and link that image to the video. You can store the file in your document library or host it directly on your site. The movie formats that can be stored in the document library are:

  • swf - Macromedia flash movie
  • flv - Flash streaming video
  • ppt - Microsoft Powerpoint
  • mpeg - MPEG video
  • mov - QuickTime video