style(all): Improve coding style (using rust-clippy)

README.md

@@ -42,7 +42,7 @@ lettre = "0.6"
 
 ## Testing
 
-The tests require an open mail server listening locally on port 25.
+The tests require an open mail server listening locally on port 25 and the `sendmail` command.
 
 ## License
 

src/email/mod.rs

@@ -267,7 +267,7 @@ pub struct EmailBuilder {
 }
 
 /// Simple email enveloppe representation
-#[derive(PartialEq,Eq,Clone,Debug)]
+#[derive(PartialEq,Eq,Clone,Debug,Default)]
 pub struct Envelope {
     /// The envelope recipients' addresses
     to: Vec<String>,
@@ -622,7 +622,7 @@ impl EmailBuilder {
         // If there are multiple addresses in "From", the "Sender" is required.
         if self.from_header.len() >= 2 && self.sender_header.is_none() {
             // So, we must find something to put as Sender.
-            for possible_sender in self.from_header.iter() {
+            for possible_sender in &self.from_header {
                 // Only a mailbox can be used as sender, not Address::Group.
                 if let &Address::Mailbox(ref mbx) = possible_sender {
                     self.sender_header = Some(mbx.clone());

src/transport/sendmail/error.rs

@@ -50,5 +50,5 @@ impl From<&'static str> for Error {
     }
 }
 
-/// SendMail result type
+/// sendmail result type
 pub type SendmailResult = Result<(), Error>;

src/transport/smtp/client/mod.rs

@@ -135,7 +135,7 @@ impl<S: Connector + Write + Read + Debug> Client<S> {
     /// Sends a MAIL command
     pub fn mail(&mut self, address: &str, options: Option<&str>) -> SmtpResult {
         match options {
-            Some(ref options) => self.command(&format!("MAIL FROM:<{}> {}", address, options)),
+            Some(options) => self.command(&format!("MAIL FROM:<{}> {}", address, options)),
             None => self.command(&format!("MAIL FROM:<{}>", address)),
         }
     }
@@ -163,7 +163,7 @@ impl<S: Connector + Write + Read + Debug> Client<S> {
     /// Sends a HELP command
     pub fn help(&mut self, argument: Option<&str>) -> SmtpResult {
         match argument {
-            Some(ref argument) => self.command(&format!("HELP {}", argument)),
+            Some(argument) => self.command(&format!("HELP {}", argument)),
             None => self.command("HELP"),
         }
     }