The main disadvantages of using a rented third-party enterprise post office for corporate users are as follows: 1) a lot of junk emails are received day by day; 2) there is nothing we can do every time something goes wrong, because most of the relevant resources are not under our control. In this case, we can try switching to MDaemon mail server. This way, not only will the received spam emails decrease significantly, but also network administrators can quickly lock down and fix problems based on the logs provided by this software on their own.