Images show in Outlook but not webmail

Every once in awhile we get a ticket from someone whose users complain that images that are sent to them inside a message -- embedded images in an HTML rich email -- show in Outlook (or another mail client) but when they look at the same message in webmail, the images are missing. 

The reason for this is actually pretty simple, and is a function of the browser and how it handles "insecure" connections. (I.e., URLs not secured with SSL - so they don't use https://, they use http://.) While most common when using Chrome, it's also possible to see this issue in the new Edge browser as it uses the same engine as Chrome.

For some time now, Chrome has prevented mixed-content web pages from displaying properly. Without getting into the technical discussion of this, think of this as Chrome blocking some page elements, such as images, from displaying if the URLs pointing to those elements aren't secured with an SSL certificate.

In many cases, Chrome can circumvent this issue by simply "upgrading" unsecured URLs to secured URLs by automatically converting the paths to use SSL. In most cases, this works as the sending domain does actually have an SSL certificate, but the specific element is just referenced improperly on the page. However, in some cases, this doesn't work because the sending server does NOT have an SSL certificate. In these cases, those elements are blocked by Chrome, so they don't display on the page. (Or in the email.)

Outlook and other clients don't have the same mixed-content restrictions. That's why the message shows fine in Outlook, say, but it doesn't display properly when viewed in Chrome.