ManageSieve: Return capabilities after successful STARTTLS

crates/managesieve/src/core/session.rs

@@ -43,6 +43,9 @@ impl SessionManager for ManageSieveSessionManager {
                 && session.instance.acceptor.is_tls()
             {
                 if let Ok(mut session) = session.into_tls().await {
+                    let _ = session
+                        .write(&session.handle_capability(SERVER_GREETING).await.unwrap())
+                        .await;
                     session.handle_conn().await;
                 }
             }