Fixed: Outlook desktop unable to render SharePoint hosted images embedded in to mail body through PowerAutomate send email action

This post comes out from a recent support experience to one of my clients. He was trying to use Microsoft PowerAutomate flow to embed a SharePoint library hosted image in to an email notification which sent regularly across the organization for all users. Usual way for doing this is using the <img src tag in the send email action but interestingly, these behaviors was a showstopper until I figured out the solution after several hours (described at the end of the article).

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Behaviors:

  1. Embedded images from a SharePoint URL did not render in Outlook desktop App
  2. Same image renders in OWA (Outlook Web App) however, there was a slight delay in loading the image.
  3. Same image hosted in public hosting locations rendered nicely as well (e.g – https://www.w3schools.com/, Google etc..)

SharePoint hosted image in Outlook Desktop App: Strange enough !

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External hosted image in Outlook Desktop App:

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Tried and did not work for my case:

  • Change the text format to HTMLOutlook client application (File -> Options -> Mail -> Compose message in HTML format). This was already in place for my scenario.
  • Add the domain to safe/trusted sites in the browser settings
  • Plethora of other solutions from Microsoft articles and forums

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The real solution:

To overcome this issue, you simply have to use these additional lines in your email step. Add a compose action and point it to ‘Get file content using path’ SharePoint action (or you can directly add this line to the mail body HTML)

Add a new Compose action in to the PowerAutomate flow 

Set the Expression as below (you can copy and paste this)

dataUri(outputs('Get_file_content_using_path')?['body'])

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Amend the Mailbody to reflect the following or add the above mentioned expression directly to the HTML body. Either way should work.

<p><br>
File content using path<br> 

<img src="@{outputs('Compose_2')}"></img>
</p>

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Full flow: Tested and working perfectly across web client and desktop client of Outlook

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Result: SharePoint hosted image is now rendered perfectly in Outlook desktop App.

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Root cause analysis:

The key point is the use of dataUri() to convert the file content to the right format that HTML can understand. An image or a file in general from a SharePoint link is not public link. Only authenticated users can view the image which is the root cause of this issue.

If a user logs in into Outlook on the web from  a browser, their Microsoft identification data are stored locally within the browser context as cookies. As a result, when opening an email that contains a SharePoint link in HTML image tags, a request will be sent to SharePoint servers with the same identification and the image can be downloaded if the user has enough privilege.

It’s the same way that if you have already logged in into one of the google services, you won’t have to login again when accessing other Google services in deferent tabs.

On the other hand, Outlook client is simply an email application which does not share the same architecture as a browser. Outlook account credentials are stored differently and Outlook does not have mechanism to detect and pass credentials to other Microsoft services. Hence, when it sees a SharePoint link in HTML image tags, a request without any authorization data will be sent to the SharePoint servers and of course, it will be refused. If a hyperlink added to the email, clicking on the link will open a browser and you will need to sign in.  In the end, the main purpose of Outlook client is for email-related tasks and it will not handle authentication for other services.