diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 457e113..e538b35 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -75,8 +75,8 @@ jobs:
             rust: stable
           - name: beta
             rust: beta
-          - name: 1.60.0
-            rust: 1.60.0
+          - name: 1.63.0
+            rust: 1.63.0
 
     steps:
       - name: Checkout
diff --git a/Cargo.toml b/Cargo.toml
index d23ea05..2247ec9 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -11,7 +11,7 @@ authors = ["Alexis Mousset <contact@amousset.me>", "Paolo Barbolini <paolo@paolo
 categories = ["email", "network-programming"]
 keywords = ["email", "smtp", "mailer", "message", "sendmail"]
 edition = "2021"
-rust-version = "1.60"
+rust-version = "1.63"
 
 [badges]
 is-it-maintained-issue-resolution = { repository = "lettre/lettre" }
diff --git a/README.md b/README.md
index d5806b5..0ccbdd4 100644
--- a/README.md
+++ b/README.md
@@ -53,12 +53,12 @@ Lettre does not provide (for now):
 ## Supported Rust Versions
 
 Lettre supports all Rust versions released in the last 6 months. At the time of writing
-the minimum supported Rust version is 1.60, but this could change at any time either from
+the minimum supported Rust version is 1.63, but this could change at any time either from
 one of our dependencies bumping their MSRV or by a new patch release of lettre.
 
 ## Example
 
-This library requires Rust 1.60 or newer.
+This library requires Rust 1.63 or newer.
 To use this library, add the following to your `Cargo.toml`:
 
 ```toml
diff --git a/src/executor.rs b/src/executor.rs
index a09851d..199a378 100644
--- a/src/executor.rs
+++ b/src/executor.rs
@@ -216,7 +216,7 @@ impl Executor for AsyncStd1Executor {
 
     #[cfg(feature = "smtp-transport")]
     fn sleep(duration: Duration) -> Self::Sleep {
-        let fut = async move { async_std::task::sleep(duration).await };
+        let fut = async_std::task::sleep(duration);
         Box::pin(fut)
     }
 
diff --git a/src/lib.rs b/src/lib.rs
index 717a338..c1eb9c7 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -6,7 +6,7 @@
 //! * Secure defaults
 //! * Async support
 //!
-//! Lettre requires Rust 1.60 or newer.
+//! Lettre requires Rust 1.63 or newer.
 //!
 //! ## Features
 //!
diff --git a/src/message/header/content.rs b/src/message/header/content.rs
index a61faf8..1220318 100644
--- a/src/message/header/content.rs
+++ b/src/message/header/content.rs
@@ -13,12 +13,14 @@ use crate::BoxError;
 /// use-caches this header shouldn't be set manually.
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+#[derive(Default)]
 pub enum ContentTransferEncoding {
     /// ASCII
     SevenBit,
     /// Quoted-Printable encoding
     QuotedPrintable,
     /// base64 encoding
+    #[default]
     Base64,
     /// Requires `8BITMIME`
     EightBit,
@@ -67,12 +69,6 @@ impl FromStr for ContentTransferEncoding {
     }
 }
 
-impl Default for ContentTransferEncoding {
-    fn default() -> Self {
-        ContentTransferEncoding::Base64
-    }
-}
-
 #[cfg(test)]
 mod test {
     use pretty_assertions::assert_eq;
diff --git a/src/transport/smtp/client/tls.rs b/src/transport/smtp/client/tls.rs
index 2824951..0fab24a 100644
--- a/src/transport/smtp/client/tls.rs
+++ b/src/transport/smtp/client/tls.rs
@@ -99,7 +99,7 @@ impl Debug for Tls {
 
 /// Source for the base set of root certificates to trust.
 #[allow(missing_copy_implementations)]
-#[derive(Clone, Debug)]
+#[derive(Clone, Debug, Default)]
 pub enum CertificateStore {
     /// Use the default for the TLS backend.
     ///
@@ -110,6 +110,7 @@ pub enum CertificateStore {
     /// enabled, or will fall back to `webpki-roots`.
     ///
     /// The boring-tls backend uses the same logic as OpenSSL on all platforms.
+    #[default]
     Default,
     /// Use a hardcoded set of Mozilla roots via the `webpki-roots` crate.
     ///
@@ -120,12 +121,6 @@ pub enum CertificateStore {
     None,
 }
 
-impl Default for CertificateStore {
-    fn default() -> Self {
-        CertificateStore::Default
-    }
-}
-
 /// Parameters to use for secure clients
 #[derive(Clone)]
 pub struct TlsParameters {