RE: Marketing email in contact timeline
Hi SkylineVS,
Based on the document, you can view that:
Along with Dynamics 365 Sales and Dynamics 365 Customer Service, you will now be able to view all your Dynamics 365 Marketing interactions in the unified activity timeline under your contacts.
Marketing app interactions automatically show up in the interactions timeline. If you don’t see interactions from the Marketing app, make sure your marketing product solution version is 1.1.10512.25 or later.
So you have checked your current form is default contact form, and version is 1.1.10512.25 or later.
Also, the contact must join these activities, You can't view any interactions in timeline if they haven't been involved.
One contact has been added to segment and involved in customer journey.