diff --git a/src/address/types.rs b/src/address/types.rs
index 6aba26e..4372daf 100644
--- a/src/address/types.rs
+++ b/src/address/types.rs
@@ -226,7 +226,7 @@ fn check_address(val: &str) -> Result<usize, AddressError> {
     Ok(user.len())
 }
 
-#[derive(Debug, PartialEq, Clone, Copy)]
+#[derive(Debug, PartialEq, Eq, Clone, Copy)]
 /// Errors in email addresses parsing
 pub enum AddressError {
     /// Missing domain or user
diff --git a/src/executor.rs b/src/executor.rs
index 99adaa7..43d31bc 100644
--- a/src/executor.rs
+++ b/src/executor.rs
@@ -109,7 +109,6 @@ impl Executor for Tokio1Executor {
     #[cfg(feature = "smtp-transport")]
     type Sleep = tokio1_crate::time::Sleep;
 
-    #[doc(hidden)]
     #[cfg(feature = "smtp-transport")]
     fn spawn<F>(fut: F) -> Self::Handle
     where
@@ -119,13 +118,11 @@ impl Executor for Tokio1Executor {
         tokio1_crate::spawn(fut)
     }
 
-    #[doc(hidden)]
     #[cfg(feature = "smtp-transport")]
     fn sleep(duration: Duration) -> Self::Sleep {
         tokio1_crate::time::sleep(duration)
     }
 
-    #[doc(hidden)]
     #[cfg(feature = "smtp-transport")]
     async fn connect(
         hostname: &str,
@@ -166,13 +163,11 @@ impl Executor for Tokio1Executor {
         Ok(conn)
     }
 
-    #[doc(hidden)]
     #[cfg(feature = "file-transport-envelope")]
     async fn fs_read(path: &Path) -> IoResult<Vec<u8>> {
         tokio1_crate::fs::read(path).await
     }
 
-    #[doc(hidden)]
     #[cfg(feature = "file-transport")]
     async fn fs_write(path: &Path, contents: &[u8]) -> IoResult<()> {
         tokio1_crate::fs::write(path, contents).await
@@ -210,7 +205,6 @@ impl Executor for AsyncStd1Executor {
     #[cfg(feature = "smtp-transport")]
     type Sleep = BoxFuture<'static, ()>;
 
-    #[doc(hidden)]
     #[cfg(feature = "smtp-transport")]
     fn spawn<F>(fut: F) -> Self::Handle
     where
@@ -220,14 +214,12 @@ impl Executor for AsyncStd1Executor {
         async_std::task::spawn(fut)
     }
 
-    #[doc(hidden)]
     #[cfg(feature = "smtp-transport")]
     fn sleep(duration: Duration) -> Self::Sleep {
         let fut = async move { async_std::task::sleep(duration).await };
         Box::pin(fut)
     }
 
-    #[doc(hidden)]
     #[cfg(feature = "smtp-transport")]
     async fn connect(
         hostname: &str,
@@ -267,13 +259,11 @@ impl Executor for AsyncStd1Executor {
         Ok(conn)
     }
 
-    #[doc(hidden)]
     #[cfg(feature = "file-transport-envelope")]
     async fn fs_read(path: &Path) -> IoResult<Vec<u8>> {
         async_std::fs::read(path).await
     }
 
-    #[doc(hidden)]
     #[cfg(feature = "file-transport")]
     async fn fs_write(path: &Path, contents: &[u8]) -> IoResult<()> {
         async_std::fs::write(path, contents).await
diff --git a/src/message/dkim.rs b/src/message/dkim.rs
index e6bf7b7..81015dc 100644
--- a/src/message/dkim.rs
+++ b/src/message/dkim.rs
@@ -96,9 +96,9 @@ impl Display for DkimSigningKeyError {
 impl StdError for DkimSigningKeyError {
     fn source(&self) -> Option<&(dyn StdError + 'static)> {
         Some(match &self.0 {
-            InnerDkimSigningKeyError::Base64(err) => &*err,
-            InnerDkimSigningKeyError::Rsa(err) => &*err,
-            InnerDkimSigningKeyError::Ed25519(err) => &*err,
+            InnerDkimSigningKeyError::Base64(err) => err,
+            InnerDkimSigningKeyError::Rsa(err) => err,
+            InnerDkimSigningKeyError::Ed25519(err) => err,
         })
     }
 }
@@ -245,7 +245,7 @@ fn dkim_canonicalize_headers_relaxed(headers: &str) -> String {
     let mut r = String::with_capacity(headers.len());
 
     fn skip_whitespace(h: &str) -> &str {
-        match h.as_bytes().get(0) {
+        match h.as_bytes().first() {
             Some(b' ' | b'\t') => skip_whitespace(&h[1..]),
             _ => h,
         }
diff --git a/src/message/header/date.rs b/src/message/header/date.rs
index c1fe98f..71e73db 100644
--- a/src/message/header/date.rs
+++ b/src/message/header/date.rs
@@ -8,7 +8,7 @@ use crate::BoxError;
 /// Message `Date` header
 ///
 /// Defined in [RFC2822](https://tools.ietf.org/html/rfc2822#section-3.3)
-#[derive(Debug, Clone, Copy, PartialEq)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub struct Date(HttpDate);
 
 impl Date {
diff --git a/src/message/header/mailbox.rs b/src/message/header/mailbox.rs
index 7ca4ba1..25c0235 100644
--- a/src/message/header/mailbox.rs
+++ b/src/message/header/mailbox.rs
@@ -14,7 +14,7 @@ pub trait MailboxesHeader {
 macro_rules! mailbox_header {
     ($(#[$doc:meta])*($type_name: ident, $header_name: expr)) => {
         $(#[$doc])*
-        #[derive(Debug, Clone, PartialEq)]
+        #[derive(Debug, Clone, PartialEq, Eq)]
         pub struct $type_name(Mailbox);
 
         impl Header for $type_name {
@@ -56,7 +56,7 @@ macro_rules! mailbox_header {
 macro_rules! mailboxes_header {
     ($(#[$doc:meta])*($type_name: ident, $header_name: expr)) => {
         $(#[$doc])*
-        #[derive(Debug, Clone, PartialEq)]
+        #[derive(Debug, Clone, PartialEq, Eq)]
         pub struct $type_name(pub(crate) Mailboxes);
 
         impl MailboxesHeader for $type_name {
diff --git a/src/message/header/special.rs b/src/message/header/special.rs
index f1a3f3b..32e5bfd 100644
--- a/src/message/header/special.rs
+++ b/src/message/header/special.rs
@@ -4,7 +4,7 @@ use crate::{
 };
 
 /// Message format version, defined in [RFC2045](https://tools.ietf.org/html/rfc2045#section-4)
-#[derive(Debug, Copy, Clone, PartialEq)]
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
 pub struct MimeVersion {
     major: u8,
     minor: u8,
diff --git a/src/message/header/textual.rs b/src/message/header/textual.rs
index bf8c628..9006547 100644
--- a/src/message/header/textual.rs
+++ b/src/message/header/textual.rs
@@ -4,7 +4,7 @@ use crate::BoxError;
 macro_rules! text_header {
     ($(#[$attr:meta])* Header($type_name: ident, $header_name: expr )) => {
         $(#[$attr])*
-        #[derive(Debug, Clone, PartialEq)]
+        #[derive(Debug, Clone, PartialEq, Eq)]
         pub struct $type_name(String);
 
         impl Header for $type_name {
diff --git a/src/transport/smtp/commands.rs b/src/transport/smtp/commands.rs
index f5d06b2..847372c 100644
--- a/src/transport/smtp/commands.rs
+++ b/src/transport/smtp/commands.rs
@@ -13,7 +13,7 @@ use crate::{
 };
 
 /// EHLO command
-#[derive(PartialEq, Clone, Debug)]
+#[derive(PartialEq, Eq, Clone, Debug)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct Ehlo {
     client_id: ClientId,
@@ -33,7 +33,7 @@ impl Ehlo {
 }
 
 /// STARTTLS command
-#[derive(PartialEq, Clone, Debug, Copy)]
+#[derive(PartialEq, Eq, Clone, Debug, Copy)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct Starttls;
 
@@ -44,7 +44,7 @@ impl Display for Starttls {
 }
 
 /// MAIL command
-#[derive(PartialEq, Clone, Debug)]
+#[derive(PartialEq, Eq, Clone, Debug)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct Mail {
     sender: Option<Address>,
@@ -73,7 +73,7 @@ impl Mail {
 }
 
 /// RCPT command
-#[derive(PartialEq, Clone, Debug)]
+#[derive(PartialEq, Eq, Clone, Debug)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct Rcpt {
     recipient: Address,
@@ -101,7 +101,7 @@ impl Rcpt {
 }
 
 /// DATA command
-#[derive(PartialEq, Clone, Debug, Copy)]
+#[derive(PartialEq, Eq, Clone, Debug, Copy)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct Data;
 
@@ -112,7 +112,7 @@ impl Display for Data {
 }
 
 /// QUIT command
-#[derive(PartialEq, Clone, Debug, Copy)]
+#[derive(PartialEq, Eq, Clone, Debug, Copy)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct Quit;
 
@@ -123,7 +123,7 @@ impl Display for Quit {
 }
 
 /// NOOP command
-#[derive(PartialEq, Clone, Debug, Copy)]
+#[derive(PartialEq, Eq, Clone, Debug, Copy)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct Noop;
 
@@ -134,7 +134,7 @@ impl Display for Noop {
 }
 
 /// HELP command
-#[derive(PartialEq, Clone, Debug)]
+#[derive(PartialEq, Eq, Clone, Debug)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct Help {
     argument: Option<String>,
@@ -158,7 +158,7 @@ impl Help {
 }
 
 /// VRFY command
-#[derive(PartialEq, Clone, Debug)]
+#[derive(PartialEq, Eq, Clone, Debug)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct Vrfy {
     argument: String,
@@ -178,7 +178,7 @@ impl Vrfy {
 }
 
 /// EXPN command
-#[derive(PartialEq, Clone, Debug)]
+#[derive(PartialEq, Eq, Clone, Debug)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct Expn {
     argument: String,
@@ -198,7 +198,7 @@ impl Expn {
 }
 
 /// RSET command
-#[derive(PartialEq, Clone, Debug, Copy)]
+#[derive(PartialEq, Eq, Clone, Debug, Copy)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct Rset;
 
@@ -209,7 +209,7 @@ impl Display for Rset {
 }
 
 /// AUTH command
-#[derive(PartialEq, Clone, Debug)]
+#[derive(PartialEq, Eq, Clone, Debug)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct Auth {
     mechanism: Mechanism,