Hi Sachin Surana, I hope you are doing good.
1. What is the difference between the two?
The mean difference between them is that Solution Only license is intended for use on development and test environments when making customizations, solving compatibility issues, importing, or exporting solutions, and doing other types of development and non-functional marketing testing. A Solution Only license is included with all paid licenses and allows you to install the Solution Only app on as many environments as needed.
2. What are the features missing in Marketing solution only?
Solution Only license includes all the entities and solutions for Dynamics 365 Marketing but doesn't include any of the marketing services. This means that marketing capabilities aren't available in this option (including email creation, email delivery, segmentation, customer journeys, and more).
3. What is recommended for installation?
If you are going to use the license for development and testing, you should choose Solution Only but if you are going to use the license for more marketing services and uses you should use the D365 Marketing Application.
Here more info that can help:
Overview (Dynamics 365 Marketing) | Microsoft Docs
Set up Dynamics 365 Marketing (Dynamics 365 Marketing) | Microsoft Docs
Thanks for your question.
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