diff --git a/Cargo.toml b/Cargo.toml
index abcdb4c..ec9e5dc 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -41,6 +41,7 @@ nom = { version = "7", optional = true }
 hostname = { version = "0.3", optional = true } # feature
 socket2 = { version = "0.5.1", optional = true }
 url = { version = "2.4", optional = true }
+percent-encoding = { version = "2.3", optional = true }
 
 ## tls
 native-tls = { version = "0.2.5", optional = true } # feature
@@ -103,7 +104,7 @@ mime03 = ["dep:mime"]
 file-transport = ["dep:uuid", "tokio1_crate?/fs", "tokio1_crate?/io-util"]
 file-transport-envelope = ["serde", "dep:serde_json", "file-transport"]
 sendmail-transport = ["tokio1_crate?/process", "tokio1_crate?/io-util", "async-std?/unstable"]
-smtp-transport = ["dep:base64", "dep:nom", "dep:socket2", "dep:url", "tokio1_crate?/rt", "tokio1_crate?/time", "tokio1_crate?/net"]
+smtp-transport = ["dep:base64", "dep:nom", "dep:socket2", "dep:url", "dep:percent-encoding", "tokio1_crate?/rt", "tokio1_crate?/time", "tokio1_crate?/net"]
 
 pool = ["dep:futures-util"]
 
diff --git a/src/transport/smtp/connection_url.rs b/src/transport/smtp/connection_url.rs
index 6ac5ee7..571adc8 100644
--- a/src/transport/smtp/connection_url.rs
+++ b/src/transport/smtp/connection_url.rs
@@ -112,7 +112,16 @@ pub(crate) fn from_connection_url<B: TransportBuilder>(connection_url: &str) ->
     }
 
     if let Some(password) = connection_url.password() {
-        let credentials = Credentials::new(connection_url.username().into(), password.into());
+        let percent_decode = |s: &str| {
+            percent_encoding::percent_decode_str(s)
+                .decode_utf8()
+                .map(|cow| cow.into_owned())
+                .map_err(error::connection)
+        };
+        let credentials = Credentials::new(
+            percent_decode(connection_url.username())?,
+            percent_decode(password)?,
+        );
         builder = builder.credentials(credentials);
     }