diff --git a/backend/00-router.go b/backend/00-router.go
index 9653ea3..d659dea 100644
--- a/backend/00-router.go
+++ b/backend/00-router.go
@@ -301,6 +301,11 @@ func emailBoxHandler(w http.ResponseWriter, r *http.Request) {
 	kind := strings.TrimPrefix(r.URL.Path, "/boxes/")
 	switch kind {
 	case "source":
+		if r.Header.Get("HX-Request") == "true" {
+			w.Header().Set("Content-Type", "text/html; charset=utf-8")
+			fmt.Fprint(w, renderEmailBoxSourcePane(accounts, r.URL.Query().Get("source")))
+			return
+		}
 		renderSourceEmailBoxPage(w, r, accounts, r.URL.Query().Get("source"))
 	case "target":
 		renderTargetEmailBoxPage(w, r, accounts)