+m.data = NULL;
+m.size = 0;
+
+if (!expand_check(tls_dhparam, US"tls_dhparam", &exp_tls_dhparam))
+ return DEFER;
+
+if (!exp_tls_dhparam)
+ {
+ DEBUG(D_tls) debug_printf("Loading default hard-coded DH params\n");
+ m.data = US std_dh_prime_default();
+ m.size = Ustrlen(m.data);
+ }
+else if (Ustrcmp(exp_tls_dhparam, "historic") == 0)
+ use_file_in_spool = TRUE;
+else if (Ustrcmp(exp_tls_dhparam, "none") == 0)
+ {
+ DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
+ return OK;
+ }
+else if (exp_tls_dhparam[0] != '/')
+ {
+ m.data = US std_dh_prime_named(exp_tls_dhparam);
+ if (m.data == NULL)
+ return tls_error(US"No standard prime named", CS exp_tls_dhparam, NULL);
+ m.size = Ustrlen(m.data);
+ }
+else
+ {
+ use_fixed_file = TRUE;
+ filename = exp_tls_dhparam;
+ }
+
+if (m.data)
+ {
+ rc = gnutls_dh_params_import_pkcs3(dh_server_params, &m, GNUTLS_X509_FMT_PEM);
+ exim_gnutls_err_check(US"gnutls_dh_params_import_pkcs3");
+ DEBUG(D_tls) debug_printf("Loaded fixed standard D-H parameters\n");
+ return OK;
+ }
+