If they can't tell you the settings to use to send email through PHP it sounds like it's time for a new host.
Maybe you just got an ignorant tech. Sometimes the really cheap hosting companies will make it hard or impossible to use features in an effort to keep costs down or claim it's a security issue. You might want to try the support forums for the host and ask what the server settings are to send email using PHP.
Note that "$WAGLOBAL_Email_Server" is just the variable used by UE. Different apps use different variables but they have the same function of setting the server to use.