Hi,

The "Send by Email" button on the invoice opens the default email template (like account.email_template_edi_invoice ) and sends the invoice as a PDF attachment to the customer.

Create a Custom Module

Create a simple custom module (eg, auto_invoice_mailer ) and add the following logic.

__manifest__.py

{
     'name' : 'Auto Invoice Email Sender' ,
     'version' : '1.0' ,
     'category' : 'Accounting' ,
     'depends' : [ 'account' ],
     'data' : [
         'data/auto_invoice_cron.xml' ,
    ],
}

models/auto_invoice.py

from odoo import models, api
 from datetime import datetime, timedelta

class  AutoInvoiceSender (models.Model):
    _inherit = 'account. move'

    @api.model 
    def  cron_send_invoices_by_email ( self ):
         # Set your criteria for invoices to send (eg, posted, customer invoice, not already sent)
        invoices = self. search([
            ( 'move_type' , '=' , 'out_invoice' ),
            ( 'state' , '=' , 'posted' ),
            ( 'invoice_date' , '>=' , (datetime.today() - timedelta(days= 30 )).date()),
            ( 'invoice_sent' , '=' , False ),   # Make sure it's not already sent
        ])

        template = self.env.ref( 'account.email_template_edi_invoice' , raise_if_not_found= False )

        for invoice in invoices:
             if template:
                invoice.message_post_with_template( template.id )
                invoice.write({ 'invoice_sent' : True })   # Mark as sent

data/auto_invoice_cron.xml

<odoo>
   <data noupdate = "1">

    <record id = "ir_cron_auto_invoice_sender"  model = "ir.cron">
       <field name = "name" >Send Monthly Customer Invoices by Email </field>
       <field name = "model_id"  ref = "account.model_account_move"/>
       <field name = "state" >code </field>
       <field name = "code" >model.cron_send_invoices_by_email() </field>
       <field name = "user_id"  ref = "base.user_admin"/>
       <field name = "interval_number">1 </field>
       <field name = "interval_type">months </field>
       <field name = "numbercall" >-1 </field>
       <field name = "doall"  eval = "False"/>
       <field name = "active" eval = "True"/>
     </record>

  </data>
 </odoo>

i hope it is usefull

Hi,

Create schedule action with the button click function.

<data noupdate="1">

     <record id="ir_cron_scheduler_recurring_action" model="ir.cron">

              <field name="name">Recurring Todo Activity</field>

               <field name="model_id" ref="model_mail_activity"/>

               <field name="state">code</field>

                <field name="code">model.action_done()</field>

                <field name="user_id" ref="base.user_root"/>

                <field name="interval_number">1</field>

                 <field name="interval_type">days</field>

                 <field name="numbercall">-1</field>

     </record>

</data>

Change the interval type as days/months

For creating email template please go through this blog

https://www.cybrosys.com/blog/creating-email-templates-in-odoo-15

Create python function to send email through button function

def action_done(self):

   mail_template = self.env.ref("module_name.email_template_name")

   mail_template_send_mail(self.id,force_send=True)

Hope it helps