-static uschar str_from_c[]="From";
-static const struct String str_from={ str_from_c, 4 };
-static uschar str_to_c[]="To";
-static const struct String str_to={ str_to_c, 2 };
-static uschar str_cc_c[]="Cc";
-static const struct String str_cc={ str_cc_c, 2 };
-static uschar str_bcc_c[]="Bcc";
-static const struct String str_bcc={ str_bcc_c, 3 };
-static uschar str_auth_c[]="auth";
-static const struct String str_auth={ str_auth_c, 4 };
-static uschar str_sender_c[]="Sender";
-static const struct String str_sender={ str_sender_c, 6 };
-static uschar str_resent_from_c[]="Resent-From";
-static const struct String str_resent_from={ str_resent_from_c, 11 };
-static uschar str_resent_to_c[]="Resent-To";
-static const struct String str_resent_to={ str_resent_to_c, 9 };
-static uschar str_fileinto_c[]="fileinto";
-static const struct String str_fileinto={ str_fileinto_c, 8 };
-static uschar str_envelope_c[]="envelope";
-static const struct String str_envelope={ str_envelope_c, 8 };
+static uschar str_from_c[] = "From";
+static const gstring str_from = { .s = str_from_c, .ptr = 4, .size = 5 };
+static uschar str_to_c[] = "To";
+static const gstring str_to = { .s = str_to_c, .ptr = 2, .size = 3 };
+static uschar str_cc_c[] = "Cc";
+static const gstring str_cc = { .s = str_cc_c, .ptr = 2, .size = 3 };
+static uschar str_bcc_c[] = "Bcc";
+static const gstring str_bcc = { .s = str_bcc_c, .ptr = 3, .size = 4 };
+#ifdef ENVELOPE_AUTH
+static uschar str_auth_c[] = "auth";
+static const gstring str_auth = { .s = str_auth_c, .ptr = 4, .size = 5 };
+#endif
+static uschar str_sender_c[] = "Sender";
+static const gstring str_sender = { .s = str_sender_c, .ptr = 6, .size = 7 };
+static uschar str_resent_from_c[] = "Resent-From";
+static const gstring str_resent_from = { .s = str_resent_from_c, .ptr = 11, .size = 12 };
+static uschar str_resent_to_c[] = "Resent-To";
+static const gstring str_resent_to = { .s = str_resent_to_c, .ptr = 9, .size = 10 };
+static uschar str_fileinto_c[] = "fileinto";
+static const gstring str_fileinto = { .s = str_fileinto_c, .ptr = 8, .size = 9 };
+static uschar str_envelope_c[] = "envelope";
+static const gstring str_envelope = { .s = str_envelope_c, .ptr = 8, .size = 9 };