When reviewing email messages that were analyzed for automatic promotion by Dynamics 365, you see an email message that failed to be created in Dynamics 365 with a InvalidSender sync error.
When Dynamics 365 evaluates an email in your mailbox, multiple conditions are evaluated to determine if the message should automatically be created as an email activity in Dynamics 365. If the evaluation results in an InvalidSender error, this indicates there was not a valid email address in the From field of the message.
Locate the corresponding email in the mailbox.
Verify there is a valid email address in the From field.
Some applications send automated emails that do not include a valid email address in the From field. For example, the Clutter feature in Outlook sends messages that result in the following informational alert:
"An error occurred while creating the incoming email "Clutter moved new and different messages" in Microsoft Dynamics 365 for the mailbox"
This alert can safely be ignored.