Temperature sensor alarm issues

Hello,
I’m stuck between a rock and a hard place on my current temperature sensor project. Everything compiles and runs as far as the web page displaying the temperatures works and runs on IP of choice ect. Now IM trying to add email alerts such

 //////////////////SUPPLY ALARMS//////////////////////////

if (supply > 20); // OVER 20 SUPPLY PROBE
Serial.print("To: email"); //To
Serial.print("From: email"); //From
Serial.print("Subject: FMS ALARM PR02!"); //Subject
Serial.print("HIGH SUPPLY TEMP"); //Body 

if (supply < 5);  // BELOW 5 SUPPLY PROBE
Serial.print("To: "email"); //To
Serial.print("From: email");//From
Serial.print("Subject: FMS ALARM PR02!"); //Subject
Serial.print("LOW SUPPLY TEMP"); //Body

and then, its just the same again another 4 times but with supply probe changing to the other 4. The skecth compiles however I get this error relating to the above code.

Any help will be much appriciated

warning: ISO C++ forbids comparison between pointer and integer [-fpermissive]

if (supply > 20); Not a syntax error, but, oops.

Please post your code- I'm going to guess that "supply" is the pointer.