php email form and checkboxes

I've created a subscription form which gathers subscribers names and details etc and adds them to a database. It also some checkboxes at the end for gathering info about what publications the user reads:

<input type="checkbox" name="Magazines[]" value="Surrey Life" />
        Surrey Life</label>
      <br />
      <label>
        <input type="checkbox" name="Magazines[]" value="The Elmbridge" />
        The Elmbridge Magazine</label>
      <br />

etc.

I've created a script which emails the form owner with the subsribers information. It also passes on the magazines that they read in the form of an array. This works but if no checkboxes are checked it returns an error message. I'm not that familiar with forms and checkboxes etc so, if someone could tell me what I need to add to correct this I'd be very grateful.

//Sending Email to form owner
$header = "From: admin@mycompany.com\n"
  . "Reply-To: admin@mycompany.com";
$subject = "Mailing List";
$email_to = "admin@mycompany.com";
foreach($_POST['Magazines'] as $value) {
$check_msg .="$value\n";
}
$body = "The following person has just been added to the mailing list\n"
. "They read the following magazines: \n $check_msg"
;
@mail($email_to, $subject ,$body ,$header ) ;