Here are the steps to have LSMTP and Hexamail coexist:
Move LSMTP to another port
1) Open LSMTP Control Program.
2) Click Configure menu item.
3) Select "SMTP & Reports" tab.
4) Change "SMTP listener port" from 25 to 2500.
5) Restart LSMTP.
Install and Configure Hexamail
1) Install Hexamail
2) You will now need to set the SMTP Server setting in Hexamail. If you are installing Hexamail on Windows, the setup program will ask you for the TCP/IP and port of your mail server during the configuration Wizard, or you can change this by opening the administration interface and setting the port on the SMTP Server settings page.
3) Next, set Hexamail SMTP Relay settings to point to your newly configured port.