I have now two custumer emails (empty ones) which are copied every 5 minutes.

It used to be just one empty mail so I thought the custumer got hacked. But now since It started to happen with a second custumer email with the same frequency I am suspecting it is a problem in our Odoo system. If I remember correctly our odoo is requesting the emails every 5 minutes and since I get 1 email of each of the custumers every 5 minutes I am guessing the error is somewhere in the system which requests the emails from our external mail server.

I am using Odoo 13 

Do you have any advice how to figure out what the problem is I am getting 2 times around 280 Opportunities every day because of this problem. It is driving me insane.