Why does a client cert imply AUTH?

[Claus Assmann]

I recently compiled mutt with SMTP/TLS support and provided a client
cert so I can successfully authenticate against my MTA. However, I
was surprised that this doesn't work: mutt asks for an account etc
and then fails with "SMTP server does not support authentication".
Well, yes, the MTA doesn't support SMTP AUTH, but it supports
authentication via a client cert just fine. I couldn't find an
option to turn AUTH off for this case, so I patched mutt a bit.
What am I missing here?

diff -r 818370d154fc mutt_ssl.c
--- a/mutt_ssl.c        Wed Oct 23 18:52:47 2013 -0700
+++ b/mutt_ssl.c        Mon Nov 25 19:40:42 2013 -0800
@@ -1087,8 +1087,10 @@
     SSL_CTX_use_certificate_file(ssldata->ctx, SslClientCert, 
SSL_FILETYPE_PEM);
     SSL_CTX_use_PrivateKey_file(ssldata->ctx, SslClientCert, SSL_FILETYPE_PEM);
 
+#ifdef USE_SASL
     /* if we are using a client cert, SASL may expect an external auth name */
     mutt_account_getuser (&conn->account);
+#endif /* USE_SASL */
   }
 }