Don't put all emails in the To header

Author: paolobarbolini

src/email.rs

@@ -41,11 +41,17 @@ fn build_email(
         .unwrap_or("test@localhost");
 
     let mut builder = Message::builder();
-    for recipient in recipients {
-        builder = builder.to(recipient.parse()?);
+
+    let mut recipients = recipients.iter();
+    let to = recipients
+        .next()
+        .ok_or_else(|| server_error("Email has no recipients"))?;
+    builder = builder.to(to.parse()?);
+    for bcc in recipients {
+        builder = builder.bcc(bcc.parse()?);
     }
-    let email = builder.from(sender.parse()?).subject(subject).body(body)?;
 
+    let email = builder.from(sender.parse()?).subject(subject).body(body)?;
     Ok(email)
 }