diff --git a/src/transport/smtp/authentication.rs b/src/transport/smtp/authentication.rs
index 90cca87..b7c874c 100644
--- a/src/transport/smtp/authentication.rs
+++ b/src/transport/smtp/authentication.rs
@@ -98,11 +98,11 @@ impl Mechanism {
                 let decoded_challenge = challenge
                     .ok_or_else(|| error::client("This mechanism does expect a challenge"))?;
 
-                if vec!["User Name", "Username:", "Username"].contains(&decoded_challenge) {
+                if ["User Name", "Username:", "Username"].contains(&decoded_challenge) {
                     return Ok(credentials.authentication_identity.clone());
                 }
 
-                if vec!["Password", "Password:"].contains(&decoded_challenge) {
+                if ["Password", "Password:"].contains(&decoded_challenge) {
                     return Ok(credentials.secret.clone());
                 }
 
diff --git a/tests/transport_stub.rs b/tests/transport_stub.rs
index 321d1f3..8bc0b4a 100644
--- a/tests/transport_stub.rs
+++ b/tests/transport_stub.rs
@@ -18,7 +18,7 @@ mod sync {
         sender_ok.send(&email).unwrap();
         sender_ko.send(&email).unwrap_err();
 
-        let expected_messages = vec![(
+        let expected_messages = [(
             email.envelope().clone(),
             String::from_utf8(email.formatted()).unwrap(),
         )];
@@ -47,7 +47,7 @@ mod tokio_1 {
         sender_ok.send(email.clone()).await.unwrap();
         sender_ko.send(email.clone()).await.unwrap_err();
 
-        let expected_messages = vec![(
+        let expected_messages = [(
             email.envelope().clone(),
             String::from_utf8(email.formatted()).unwrap(),
         )];
@@ -75,7 +75,7 @@ mod asyncstd_1 {
         sender_ok.send(email.clone()).await.unwrap();
         sender_ko.send(email.clone()).await.unwrap_err();
 
-        let expected_messages = vec![(
+        let expected_messages = [(
             email.envelope().clone(),
             String::from_utf8(email.formatted()).unwrap(),
         )];