Odoo 19.0
CRM
When a user attempts to send a message from a CRM record (Opportunity/Lead) and no recipient is selected (no followers or email address), the system will display an error message:
"You cannot send a message without at least one recipient."
The message will not be sent until a valid recipient is added.
This validation applies only to the CRM module and does not affect other applications like Discuss, Sales, or Accounting.

