First of all, you are not reusing your variable $from anywhere in your code. This isn't the cause of the error, but just setting a variable and then forgetting it wastes memory.
The error may come from this line of your code
$headers .= "Computerman Site";
"Computerman Site" is NOT a valid message header. It should look like "From: email@ddress.example.com" or "From: Someone's website <someone@example.net>". You must provide an e-mail address if you add the From field.
The error may come from this line of your code
$headers .= "Computerman Site";
"Computerman Site" is NOT a valid message header. It should look like "From: email@ddress.example.com" or "From: Someone's website <someone@example.net>". You must provide an e-mail address if you add the From field.