This error can be seen in Dynamics 365 Online Ver. 8.2 only. This does not occur with Dynamics CRM Online 2016 Update 1.

The error occurs when followings are met.

1. When creating a Contact record, you will have the same value in [Full Name] and [E-mail] fields.


2. Go to Settings > Administration > System Settings > Email tab > Set Email form options


3. Set “Allow messages with unresolved email recipients to be sent” to YES


4. When sending an email from Activity entity, enter the email address that was saved from above steps to TO field gets an error.

*Same error in CC and BCC

Turning on the legacy form rendering can be a workaround which is not going to be supported anymore.

Please fix this issue.