feat(all): Merge lettre_email into lettre with a builder feature

benches/transport_smtp.rs

@@ -0,0 +1,52 @@
+use criterion::{black_box, criterion_group, criterion_main, Criterion};
+use lettre::{
+    smtp::ConnectionReuseParameters, ClientSecurity, EmailAddress, Envelope, SendableEmail,
+    SmtpClient, Transport,
+};
+
+fn bench_simple_send(c: &mut Criterion) {
+    let mut sender = SmtpClient::new("127.0.0.1:2525", ClientSecurity::None)
+        .unwrap()
+        .transport();
+
+    c.bench_function("send email", move |b| {
+        b.iter(|| {
+            let email = SendableEmail::new(
+                Envelope::new(
+                    Some(EmailAddress::new("user@localhost".to_string()).unwrap()),
+                    vec![EmailAddress::new("root@localhost".to_string()).unwrap()],
+                )
+                .unwrap(),
+                "id".to_string(),
+                "Hello ß☺ example".to_string().into_bytes(),
+            );
+            let result = black_box(sender.send(email));
+            assert!(result.is_ok());
+        })
+    });
+}
+
+fn bench_reuse_send(c: &mut Criterion) {
+    let mut sender = SmtpClient::new("127.0.0.1:2525", ClientSecurity::None)
+        .unwrap()
+        .connection_reuse(ConnectionReuseParameters::ReuseUnlimited)
+        .transport();
+    c.bench_function("send email with connection reuse", move |b| {
+        b.iter(|| {
+            let email = SendableEmail::new(
+                Envelope::new(
+                    Some(EmailAddress::new("user@localhost".to_string()).unwrap()),
+                    vec![EmailAddress::new("root@localhost".to_string()).unwrap()],
+                )
+                .unwrap(),
+                "id".to_string(),
+                "Hello ß☺ example".to_string().into_bytes(),
+            );
+            let result = black_box(sender.send(email));
+            assert!(result.is_ok());
+        })
+    });
+}
+
+criterion_group!(benches, bench_simple_send, bench_reuse_send);
+criterion_main!(benches);