¡Hola desde Valencia!

I tried your solution. The e-mail arrived in Odoo, but Odoo replied with an error mail.

The message couldn't be accepted by Odoo.

Translations from Dutch to English:

offerte = quotation

verkooporder = salesorder

Jan

You can create an alias. Menú: (Debug mode) Settings / Technical / Aliases

When Odoo receives an email on the alias address creates a record in the "Aliased Model", puts the email text on the chatter and adds the attached files. 

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ASWER EDITED 30/08/2024:

As colleagues say, the above proposal raises an error. The "sale.order" model requires the partner as a mandatory value.

I propose to create a generic client to be able to create the record and set the ID of this client as the default value in the mail alias.

I tested it and it works. 

The only issue is that the "name" field of the order is filled with the subject of the mail and not using the sequence. 

If this is a problem, it can be solved with a custom module or an automated action.