Unexpected error is throwing when User clicks the mark as Shipped in the Item fulfillment.

The error is typically caused by an invalid email address in the “To Be E-mailed” field on the associated sales order. An invalid email address may include:
- Incomplete formats, such as missing domain extensions (e.g., “support@netsuite instead of “support@netsuite.com”).
- Extra characters or trailing spaces after the domain (e.g., “support@netsuite.com “).

Solution
To resolve this issue, you must update the invalid email address on the sales order.