Since Sitecore EXM 3.0 was released, we are able to show our own Sitecore EXM email template on the shining EXM UI.
For example, I create a new one-time message template called New User and I want it to be displayed as below.
To achieve this, I need to switch to the core database and go to /sitecore/client/Applications/ECM/Component/Create/One Time/.
From there, I create a new item based on CreateMessageSection template. Later, I can save all my one-time message templates in this section.
I need to give a name to the new section and make it visible. The index field allows me to change the position of the section on the EXM UI.
To create my New User template thumbnail, I use the CreateMessageOption template.
I get more fields to fill out this time.
Name: The template name on the UI.
IconUrl: The URL of the thumbnail to be displayed on the UI. The EXM's default thumbnails can be found at /sitecore/client/Applications/ECM/Assets/Thumbnails/
Parameters: This field uses JSON syntax and needs to include the messageTemplateId and the messageTypeTemplateId. In this post, the messageTemplateId is the NewUser template Id, the messageTypeTemplateId is the One time message type template Id, which is located at /sitecore/templates/Email Campaign/Message Types/OneTime in the master database.
Url: This field points to the page that EXM will redirect to when the thumbnail is clicked. This can be a customized page or the default EXM one time message page, /sitecore/client/Applications/ECM/Pages/Messages/OneTime
Visible: Make the thumbnail to be displayed on the UI.
SectionIndex: The position of the thumbnail in the section.
That's it :-)