Open the existing email server behavior. Click the Configure Mail Settings button in the toolbar. You can set the port and server details there. See attached screenshot for an example.
The SPF record needs to be added to your domain DNS, so you would need to login to your domain control panel to do this.
All of this is academic though if you have been using an old version of PHP on your old host - if your new host is using PHP7 or 8, you must update your connections and mySQLi behaviors as mentioned previously in this thread. The email code will not work otherwise.