from odoo import api, fields, models class MailComposeMessage(models.TransientModel): _inherit = 'mail.compose.message' @api.multi def get_mail_values(self, res_ids): """Generate the values that will be used by send_mail to create mail_messages or mail_mails. """ results = super(MailComposeMessage, self).get_mail_values(res_ids) for res_id in res_ids: results[res_id]['mail_activity_type_id'] = self.mail_activity_type_id.id return results