Hi,

In Odoo 18 Enterprise, unknown email addresses appearing in your Contacts list are often created automatically when Odoo processes incoming emails or imports data from external sources such as web forms or integrations. Whenever Odoo encounters a new email address in a message, lead, or document, it generates a new contact record, which explains why these unfamiliar entries appear.

You cannot delete these contacts directly because they are linked to other records, as indicated by the validation error referencing sale_order_partner_id_fkey. To resolve this, you can either archive the contacts to hide them while keeping your data intact or reassign their related records (like sales orders or leads) to the correct contact before deleting them.

It’s also advisable to review your email gateway and system integrations to ensure that Odoo isn’t unintentionally creating contacts from incoming emails or catchall addresses. Disabling unnecessary automatic contact creation will help prevent this issue from recurring.

Hope it helps

The error is telling you these Contacts are linked to Sales Orders.

Perhaps abandoned carts from eCommerce?