Do not ask for ESMTP credentials if unable to handle them.

* libproto/mailer/smtp.c (smtp_open): Disable ESTMP AUTH if
GSASL support is not compiled.
* libproto/mailer/smtp_auth.c (mu_smtp_auth): If compiled
without GSASL, don't attempt to obtain user credentials.

@@ -134,6 +134,16 @@ smtp_mailer_add_auth_mech (struct _smtp_mailer *smtp_mailer, const char *str)
     }
 }
 
+/* FIXME: So far, ESMTP AUTH support is available only if MU is compiled
+   with GNU SASL. Should this change, the define below must be changed
+   as well. See also smtp_auth.c.
+ */
+#ifdef WITH_GSASL
+# define DFLNOAUTH 0
+#else
+# define DFLNOAUTH 1
+#endif
+
 static int
 smtp_open (mu_mailer_t mailer, int flags)
 {
@@ -144,7 +154,7 @@ smtp_open (mu_mailer_t mailer, int flags)
   char **parmv = NULL;
   int tls = 0;
   int nostarttls = 0;
-  int noauth = 0;
+  int noauth = DFLNOAUTH;
 
   rc = mu_url_sget_scheme (mailer->url, &scheme);
   if (rc == 0) 

@@ -112,6 +112,7 @@ mu_smtp_auth (mu_smtp_t smtp)
   if (smtp->state != MU_SMTP_MAIL)
     return MU_ERR_SEQ;
 
+#if defined(WITH_GSASL)
   /* Obtain missing authentication credentials either from the
      URL (when supplied) or from the user ticket file, or by
      asking the user, if anything else fails.
@@ -126,10 +127,11 @@ mu_smtp_auth (mu_smtp_t smtp)
   _mu_smtp_fixup_params (smtp);
   if (!smtp->param[MU_SMTP_PARAM_USERNAME] && !smtp->secret)
     return MU_ERR_AUTH_NO_CRED;
-#if defined(WITH_GSASL)
   return _mu_smtp_gsasl_auth (smtp);
 #else
-  /* FIXME: Provide support for some basic authentication methods */
+  /* FIXME: Provide support for some basic authentication methods.
+     Once done, make sure _mu_smtp_fixup_params is called for this
+     branc as well (though see the fixme above). */
   return ENOSYS;
 #endif
 }