What is data URI support, as in the main mail client?

Question

Data URIs are a standard way to embed images and other binary data in HTML, and browser support is well documented on the Internet. (IE8 was the first version of IE to support data URIs with a maximum size of 32 KB per URI; other major browsers supported it even longer.)

My question is about desktop emails and webmail software.

When creating HTML email, it’s standard practice to include images as attachments or upload them externally (i.e. track images). Both of them have drawbacks (some clients list all of these attached files, and many correctly block or require user action to view external images). Thus, a data URI looks like a good way, but only if it is supported by email readers.

So, does anyone have a link to a recent study supporting this feature? Or have you researched this at all? For example, here is an overview of CSS support . Client software that I would be interested in includes:

Desktop (including version information): Outlook, Apple Mail, Thunderbird, Evolution, Lotus Notes, AOL, Eudora

Webmail: Gmail, Live / Hotmail, Yahoo! Mail, AOL

Mobile: Android, iPhone

Answer 1

I did a more recent test on Litmus , with data URIs for inline <img> elements and css background images.

These desktop clients display data URIs:

• Apple Mail 5
• Apple Mail 6
• Lotus notes 8
• Outlook 2003
• Thunderbird 3.0
• Thunderbird latest

These mobile clients display data URIs:

• Android 2.3
• Android 4.0
• Blackberry 5 OS
• IPad
• iPhone 3GS
• iPhone 4S
• iPhone 5

None of the webmail clients showed a data URI.

These desktop clients do not:

• Lotus Notes 6.5
• Lotus notes 7
• Lotus Notes 8.5
• Outlook 2000
• Outlook 2002 / XP
• Outlook 2007
• Outlook 2010
• Outlook 2011
• Outlook 2013

These mobile clients do not:

• Gmail (Android)
• Outlook.com (Android)
• Yahoo (Android)
• Blackberry 4 OS
• Symbian
• Windows Phone 7.5

Answer 2

I just checked GMail, and it looks like GMail no longer supports data URIs.

In addition, gmx.de (a very popular German webmail provider) converts image URIs to URIs on its server, and this does not seem to support data URIs.

Answer 3

Mac Mail, Outlook 2003, and MobileMe support data URIs. Not sure about other clients, but you can easily find out - create a new message in Gmail, click "Insert Image", then click "Use URL" and paste in the data URI. Then send it to several addresses and open it in the desired clients.

Answer 4

I cannot answer the question about uri data support directly, but support for something like this is often very poor in mail browsers. The problem is really related to many of them, using their own rendering rendering mechanisms, which are not fully functional html-rendering. On a system that is still preferable to using tabular design to make sure emails are readable, I would not do anything clever.

However, you may already know that email allows two types of binding. If you mark an attachment as inline, then it does not appear in the list of attachments (although this often happens).

I would personally think that providing email readability is better than not showing, and obviously, a different approach to deleted images does not help here.