Many Dynamics 365 (formerly Dynamics CRM) solutions involve external or occasional users who do not need access to the full Dynamics 365 user interface and would be better served with a simplified view of selected forms and reports.
Here are some products that provide portal functionality for Dynamics 365:
Power Apps Portal
Power Apps Portal is Microsoft's portal companion to Dynamics 365. In September 2015, Microsoft acquired Adxstudio which had long been providing a portal for Dynamics CRM and a less powerful, free version under the auspices of Microsoft.Microsoft used Adxstudio as the basis of its latest portal product, Dynamics 365 Portal which is available for Dynamics 365 users as part of the Plan 1 subscription bundle.
The Portal Connector
Pavliks offers The Portal Connector for Dynamics CRM based on Telerik Sitefinity. The Portal Connector is priced at $14,995 ($3,000 of which is for the Sitefinity software license) with an optional e-commerce connector for $7,000.
Because The Portal Connector is based on Sitefinity, you also end up with a complete content management system for your website.
Microsoft has discontinued development of Adxstudio, but made it available on GitHub for on premises implementations.