Improve DNS interface. Number of MXs used in various operations is configurable.

* mfd/dnsbase.c (_getmx): Change prototype. Use struct mxbuf,
(dns_get_mx_records): Likewise.
(dns_freemx): Remove.
(mxbuf_init, mxbuf_free): New functions.
* mfd/dns.h (mxbuf): New struct.
(mxbuf_t): Remove typedef.
(mxbuf_init, mxbuf_free): New functions.
(dns_get_mx_records): Change proto.
(dns_freemx): Remove proto.
* mfd/dnscache.c (parse_value, dns_cache_get): Change signature. All callers
updated.
* mfd/mailfromd.h (getmx, getmxip): Change signature.
(max_callout_mx, max_match_mx): New externs.
(dns_cache_get): Change signature.
* mfd/main.c (max_callout_mx, max_match_mx): New globals.
(mf_cfg_param): New statements "max-callout-mx" and "max-match-mx".
* mfd/callout.c (callout_mx): Use new mxbuf interface.
* mfd/dns.c (getmx): Change signature. Use new mxbuf interface.
(getmxip): Likewise.
* mfd/prog.c (mx_match): Use new mxbuf interface. Limit number
of MXs by max_match_mx.
* mfd/spf.c (mech_mx): Use new mxbuf interface.

* mfd/builtin/dns.bi (dns_cfg_param): New statement "max-dns-reply-mx".
(primitive_hasmx,getmx)
(primitive_ismx): Rewrite to use new mxbuf interface.

* doc/values.texi (MAX_DNS_MX, MAXMXCOUNT): New values.
* doc/functions.texi: Update.
* doc/mailfromd.texi: Update.
* doc/pmult.texi: Update.
* doc/values.texi (MAX_DNS_MX, MAXMXCOUNT): New values.

14 files changed, 219 insertions, 96 deletions

diff --git a/doc/functions.texi b/doc/functions.texi
index 51b4a8ff..4e227e41 100644
--- a/doc/functions.texi
+++ b/doc/functions.texi
@@ -1444,8 +1444,10 @@ getmx("org.pl") @result{} ""
 
 @emph{Notes}:
 @enumerate 1
-@item The @code{getmx} function returns at most 32 @acronym{MX} names or @acronym{IP} addresses.
-@FIXME{This limit should be configurable.}
+@item The number of @acronym{MX} names or @acronym{IP} addresses
+returned by @code{getmx} is limited by the value of
+@code{max-dns-reply-mx} configuration statement (default
+@value{MAX_DNS_MX}).  @xref{conf-runtime, max-dns-reply-mx}.
 
 @item The number of items returned by @code{getmx(@var{domain})} can
 differ from that obtained from @code{getmx(@var{domain}, 1)}, e.g.:
@@ -1541,6 +1543,10 @@ exception @code{e_not_found}.
 
   If @acronym{DNS} query fails, the function raises @code{failure} or
 @code{temp_failure}, depending on the character of the failure.
+
+  The number of @samp{MX} records examined by this function is limited
+by the value of the @code{max-dns-reply-mx} configuration statement
+(@pxref{conf-runtime, max-dns-reply-mx}.
 @end deftypefn
 
 @anchor{ismx}
@@ -1553,7 +1559,11 @@ is a host name or @acronym{IP} address.
 records for the @var{domain}.  Otherwise it returns @code{false}.
 
   If @var{domain} has no @samp{MX} records, or if the @acronym{DNS} query fails, the
-function returns @code{false}. 
+function returns @code{false}.
+
+  The number of @samp{MX} records examined by this function is limited
+by the value of the @code{max-dns-reply-mx} configuration statement
+(@pxref{conf-runtime, max-dns-reply-mx}.
 @end deftypefn
 
 @deftypefn {Built-in Function} string primitive_resolve (string @var{host}, @
diff --git a/doc/mailfromd.texi b/doc/mailfromd.texi
index 57e2fbb6..74f9a5a8 100644
--- a/doc/mailfromd.texi
+++ b/doc/mailfromd.texi
@@ -309,6 +309,7 @@ Configuring @command{mailfromd}
 * conf-priv::       Privilege Configuration
 * conf-database::   Database Configuration
 * conf-runtime::    Runtime Constants
+* conf-other::      Other Configuration Statements
 * conf-mailutils::  Standard Mailutils Statements
 
 @command{Mailfromd} Command Line Syntax
@@ -5367,7 +5368,7 @@ certain restrictions on the statements that can be used within them:
 @cindex @code{return} in @samp{end}
 @cindex @samp{end} and @code{return}
 @item @code{return} cannot be used in @samp{begin} and @samp{end}
-handlers. @FIXME{It could be a useful feature, though.}
+handlers.
 
 @cindex @code{accept} in @samp{begin}
 @cindex @samp{begin} and @code{accept}
@@ -6071,6 +6072,7 @@ $f fnmatches "*org*" @result{} @code{true}
 @end group
 @end smallexample
 
+@anchor{mx matches}
 @cindex mx matches
   Both operators have a special form, for @dfn{@samp{MX} pattern matching}.
 The expression:
@@ -6098,6 +6100,10 @@ returns true.  Otherwise, its result is false.
 returns true only if any of the @samp{MX}s for (domain or email) @var{x}
 match the globbing pattern @var{y}.
 
+  These operators examine at most @value{MAXMXCOUNT} @samp{MX}
+records.  To change this limit, use the @code{max-match-mx}
+configuration statement (@pxref{conf-other, max-match-mx}).
+
   Both @code{mx matches} and @code{mx fnmatches} can signal the
 following exceptions: @code{e_temp_failure}, @code{e_failure}.
 
@@ -7484,7 +7490,7 @@ can be used in complex scripts to create non-local exits from deeply
 nested statements. @FIXME{Elaborate on that.}
 
   Notice, that the the @var{excode} argument must be an immediate
-value: an exception identifier (either built-in one or one declared
+value: an exception identifier (either a built-in one or one declared
 previously using a @code{dclex} statement).
   
 @node Polling
@@ -8602,6 +8608,7 @@ Mailutils Manual}.
 * conf-priv::       Privilege Configuration
 * conf-database::   Database Configuration
 * conf-runtime::    Runtime Constants
+* conf-other::      Other Configuration Statements
 * conf-mailutils::  Standard Mailutils Statements
 @end menu
 
@@ -9049,6 +9056,11 @@ setvar mailfrom_address @var{string};
 @end smallexample
 @end deffn
 
+@deffn {Mailfromd Conf} max-callout-mx number
+  Sets the maximum number of MXs to be polled during a callout
+verification.  Defaults to @value{MAXMXCOUNT}.
+@end deffn
+
 @node conf-priv
 @section Privilege Configuration
 
@@ -9188,6 +9200,22 @@ returned in a reply.  This affects the @code{dns_getname} function
 (@pxref{DNS functions, dns_getname}).  The default value is @value{MAX_DNS_PTR}.
 @end deffn
 
+@deffn {runtime} max-dns-reply-mx number
+Sets the maximum number of @acronym{DNS} @samp{MX} records to be
+returned in a reply.  This affects the following functions:
+@code{getpx}, @code{ismx}, @code{primitive_mx}
+(@pxref{DNS functions}).  The default value is @value{MAX_DNS_MX}.
+@end deffn
+
+@node conf-other
+@section Other Configuration Statements
+
+@deffn {Mailfromd Conf} max-match-mx number
+Sets the maximum number of MXs to use in @samp{mx matches} operations
+(@pxref{mx matches}).  Defaults to @value{MAXMXCOUNT}.
+@end deffn
+
+
 @node conf-mailutils
 @section Standard Mailutils Statements
 
diff --git a/doc/pmult.texi b/doc/pmult.texi
index bf9bfb08..4c5af1ea 100644
--- a/doc/pmult.texi
+++ b/doc/pmult.texi
@@ -161,8 +161,7 @@ always @samp{1}.  Defined in @code{envfrom} and subsequent handlers.
 
 @item nrcpts
 The number of validated recipients for a single message.  Defined in
-@code{envfrom} and @code{envrcpt} handlers.  @FIXME{Verify if it
-matches this semantics.}
+@code{envfrom} and @code{envrcpt} handlers.
 
 @item r
 Protocol used to receive the message.  The value of this macro is
diff --git a/doc/values.texi b/doc/values.texi
index 6d83ef47..c9c655d9 100644
--- a/doc/values.texi
+++ b/doc/values.texi
@@ -16,3 +16,5 @@
 @set NMSGS 1024
 @set MAX_DNS_A 64
 @set MAX_DNS_PTR 64
+@set MAX_DNS_MX 32
+@set MAXMXCOUNT 32
diff --git a/mfd/builtin/dns.bi b/mfd/builtin/dns.bi
index 9f4eed65..6782edf9 100644
--- a/mfd/builtin/dns.bi
+++ b/mfd/builtin/dns.bi
@@ -21,11 +21,14 @@
 
 static size_t max_ptr = 64;
 static size_t max_a = 64;
+static size_t max_mx = MAXMXCOUNT;
 static struct mu_cfg_param dns_cfg_param[] = {
 	{ "max-dns-reply-a", mu_cfg_size, &max_a, 0, NULL,
 	  N_("Maximum number of A records in a DNS reply.") },
 	{ "max-dns-reply-ptr", mu_cfg_size, &max_a, 0, NULL,
 	  N_("Maximum number of PTR records in a DNS reply.") },
+	{ "max-dns-reply-mx", mu_cfg_size, &max_mx, 0, NULL,
+	  N_("Maximum number of MX records in a DNS reply.") },
 	{ NULL }
 };
 
@@ -173,18 +176,18 @@ END
 
 MF_DEFUN(primitive_hasmx, NUMBER, STRING string)
 {
-	mxbuf_t mxbuf;
+	struct mxbuf mxbuf;
 	mf_status mxstat;
 
-	mxstat = getmx(string, mxbuf);
+	mxbuf.mx_flags = 0;
+	mxstat = getmx(string, &mxbuf);
 	
 	MF_ASSERT(mxstat == mf_success || mxstat == mf_not_found,
 		  mf_status_to_exception(mxstat),
 		  _("cannot get MX records for %s"),
 		  string);
-
+	mxbuf_free(&mxbuf);
 	if (mxstat == mf_success) {
-		dns_freemx(mxbuf);
 		MF_RETURN(1);
 	}
 	MF_RETURN(0);
@@ -196,16 +199,20 @@ MF_DEFUN(getmx, STRING, STRING domain, OPTIONAL, NUMBER no_resolve)
 	mf_status mxstat;
 
 	if (MF_OPTVAL(no_resolve)) {
-		GACOPYZ_UINT32_T ipbuf[MAXMXCOUNT];
+		GACOPYZ_UINT32_T *ipbuf;
 		size_t ipcount;
-		
-		mxstat = getmxip(domain, ipbuf, &ipcount);
-		MF_ASSERT(mxstat == mf_success || mxstat == mf_not_found,
-			  mf_status_to_exception(mxstat),
-			  _("cannot get MX records for %s"), domain);
-		if (mxstat == mf_not_found)
+
+		ipbuf = xcalloc(max_mx, sizeof(ipbuf[0]));
+		mxstat = getmxip(domain, ipbuf, max_mx, &ipcount);
+		if (!mf_resolved(mxstat)) {
+			free(ipbuf);
+			MF_THROW(mf_status_to_exception(mxstat),
+				 _("cannot get MX records for %s"), domain);
+		}
+		if (mxstat == mf_not_found) {
+			free(ipbuf);
 			MF_RETURN_STRING("");
-		else {
+		} else {
 			int i;
 			
 			MF_OBSTACK_BEGIN();
@@ -217,26 +224,35 @@ MF_DEFUN(getmx, STRING, STRING domain, OPTIONAL, NUMBER no_resolve)
 					MF_OBSTACK_1GROW(' ');
 				MF_OBSTACK_GROW(inet_ntoa(s));
 			}
+			free(ipbuf);
 			MF_OBSTACK_1GROW(0);
 			MF_RETURN_OBSTACK();
 		}
 	} else {
-		mxbuf_t mxbuf;
-		
-		mxstat = getmx(domain, mxbuf);
-		if (mxstat == mf_not_found)
+		struct mxbuf mxbuf;
+
+		mxbuf.mx_max = max_mx;
+		mxbuf.mx_flags = MXF_MAX;
+		mxstat = getmx(domain, &mxbuf);
+		if (!mf_resolved(mxstat)) {
+			mxbuf_free(&mxbuf);
+			MF_THROW(mf_status_to_exception(mxstat),
+				 _("cannot get MX records for %s"), domain);
+		}
+		if (mxstat == mf_not_found) {
+			mxbuf_free(&mxbuf);
 			MF_RETURN_STRING("");
-		else {
+		} else {
 			int i;
 		
 			MF_OBSTACK_BEGIN();
-			for (i = 0; i < MAXMXCOUNT && mxbuf[i]; i++) {
+			for (i = 0; i < mxbuf.mx_cnt; i++) {
 				if (i > 0)
 					MF_OBSTACK_1GROW(' ');
-				MF_OBSTACK_GROW(mxbuf[i]);
+				MF_OBSTACK_GROW(mxbuf.mx_buf[i]);
 			}
 			MF_OBSTACK_1GROW(0);
-			dns_freemx(mxbuf);
+			mxbuf_free(&mxbuf);
 			MF_RETURN_OBSTACK();
 		}
 	}
@@ -272,7 +288,7 @@ resolve_host(const char *string, unsigned long *ip)
 
 MF_DEFUN(primitive_ismx, NUMBER, STRING domain, STRING ipstr)
 {
-	GACOPYZ_UINT32_T ipbuf[MAXMXCOUNT];
+	GACOPYZ_UINT32_T *ipbuf;
 	size_t ipcount;
 	mf_status mxstat;
 	unsigned long ip;
@@ -282,12 +298,15 @@ MF_DEFUN(primitive_ismx, NUMBER, STRING domain, STRING ipstr)
 	MF_ASSERT(resolve_host(ipstr, &ip) == 0, mfe_noresolve, 
                   _("cannot resolve host name %s"), ipstr);
 	ip = ntohl(ip);
-	
-	mxstat = getmxip(domain, ipbuf, &ipcount);
-	
-	MF_ASSERT(mxstat == mf_success,
-		  mf_status_to_exception(mxstat),
-		  _("cannot get MXs for %s"), domain);
+
+	ipbuf = xcalloc(max_mx, sizeof(ipbuf[0]));
+	mxstat = getmxip(domain, ipbuf, max_mx, &ipcount);
+
+	if (mxstat != mx_success) {
+		free(ipbuf);
+		MF_THROW(mf_status_to_exception(mxstat),
+			 _("cannot get MXs for %s"), domain);
+	}
 
 	for (i = 0; i < ipcount; i++) {
 		if (ipbuf[i] == ip) {
@@ -295,6 +314,8 @@ MF_DEFUN(primitive_ismx, NUMBER, STRING domain, STRING ipstr)
 			break;
 		}
 	}
+		
+	free(ipbuf);
 	MF_RETURN(rc);
 }
 END
diff --git a/mfd/callout.c b/mfd/callout.c
index 3d701577..57d0c3a6 100644
--- a/mfd/callout.c
+++ b/mfd/callout.c
@@ -591,8 +591,12 @@ mf_status
 callout_mx(struct smtp_io_data *iop, const char *hostname, int *pcount)
 {
 	int i;
-	mxbuf_t mxbuf;
-	mf_status rc, mxstat = getmx(hostname, mxbuf);
+	struct mxbuf mxbuf;
+	mf_status rc, mxstat;
+
+	mxbuf.mx_max = max_callout_mx;
+	mxbuf.mx_flags = MXF_MAX;
+	mxstat = getmx(hostname, &mxbuf);
 
 	if (pcount)
 		*pcount = 0;
@@ -600,23 +604,20 @@ callout_mx(struct smtp_io_data *iop, const char *hostname, int *pcount)
 	case mf_success:
 		debug1(2,"Checking MX servers for %s", iop->email);
 		rc = mf_not_found;
-		for (i = 0; i < MAXMXCOUNT && mxbuf[i]; i++) {
-			rc = callout_host(iop, mxbuf[i]);
+		for (i = 0; i < mxbuf.mx_cnt; i++) {
+			rc = callout_host(iop, mxbuf.mx_buf[i]);
 			if (mf_resolved(rc))
 				break;
 		}
-		if (pcount) {
-			for (; i < MAXMXCOUNT && mxbuf[i]; i++)
-				;
-			*pcount = i;
-		}
-		dns_freemx(mxbuf);
+		if (pcount)
+			*pcount = mxbuf.mx_cnt;
 		break;
 		
 	default:
 		rc = mxstat;
 		break;
 	}
+	mxbuf_free(&mxbuf);
 	return rc;
 }
 
diff --git a/mfd/dns.c b/mfd/dns.c
index 828665fc..46bdfc02 100644
--- a/mfd/dns.c
+++ b/mfd/dns.c
@@ -37,17 +37,22 @@ dns_to_mf_status(dns_status stat)
 }
 
 mf_status
-getmx(const char *host, mxbuf_t mxbuf)
+getmx(const char *host, struct mxbuf *mxbuf)
 {
-	mf_status rc = dns_cache_get(T_MX, host, mxbuf, MAXMXCOUNT);
+	mf_status rc;
+
+	mxbuf_init(mxbuf);
+	rc = dns_cache_get(T_MX, host, mxbuf->mx_buf, mxbuf->mx_max,
+			   &mxbuf->mx_cnt);
 	if (!mf_resolved(rc)) {
 		dns_status status;
 		unsigned long ttl;
 		size_t mxcnt;
 		
-		status = dns_get_mx_records(host, 1, mxbuf, &mxcnt, &ttl);
+		status = dns_get_mx_records(host, 1, mxbuf, &ttl);
 		if (status == dns_success) 
-			dns_cache_put(T_MX, host, ttl, mxbuf, mxcnt);
+			dns_cache_put(T_MX, host, ttl,
+				      mxbuf->mx_buf, mxbuf->mx_cnt);
 		else
 			dns_cache_put(T_MX, host, 0, NULL, 0);
 		rc = dns_to_mf_status(status);
@@ -56,36 +61,38 @@ getmx(const char *host, mxbuf_t mxbuf)
 }
 
 mf_status
-getmxip(char *host, GACOPYZ_UINT32_T ipbuf[MAXMXCOUNT], size_t *pcount)
+getmxip(char *host, GACOPYZ_UINT32_T *ipbuf, size_t mxmax, size_t *pcount)
 {
-	mxbuf_t mxbuf;
+	struct mxbuf mxbuf;
 	mf_status mxstat;
 	size_t ipcount;
 	size_t i;
 
-	mxstat = getmx(host, mxbuf);
+	mxbuf.mx_max = mxmax;
+	mxbuf.mx_flags = MXF_MAX;
+	mxstat = getmx(host, &mxbuf);
 	if (mxstat != mf_success)
 		return mxstat;
 
 	ipcount = 0;
-	for (i = 0; i < MAXMXCOUNT && mxbuf[i]; i++) {
+	for (i = 0; i < mxbuf.mx_cnt; i++) {
 		size_t ipn;
-		mf_status stat = a_lookup(mxbuf[i],
+		mf_status stat = a_lookup(mxbuf.mx_buf[i],
 					  ipbuf + ipcount,
-					  MAXMXCOUNT - ipcount,
+					  mxmax - ipcount,
 					  &ipn,
 					  NULL, NULL, 0);
 		if (stat == mf_success) {
 			size_t n;
-			for (n = 0; ipcount < MAXMXCOUNT && n < ipn;
+			for (n = 0; ipcount < mxmax && n < ipn;
 			     n++, ipcount++) 
 				ipbuf[ipcount] = ntohl(ipbuf[ipcount]);
-			if (ipcount == MAXMXCOUNT)
+			if (ipcount == mxmax)
 				break;
 		}
 	}
 	
-	dns_freemx(mxbuf);
+	mxbuf_free(&mxbuf);
 	*pcount = ipcount;
 	return mf_success;
 }
@@ -101,7 +108,7 @@ resolve_ipstr_domain(const char *ipstr, const char *domain, char **phbuf)
 		answer = xmalloc(MAXPACKET);
 	debug1(80,"Getting canonical name for %s", ipstr);
 
-	status = dns_cache_get(T_PTR, ipstr, &hbuf, 1);
+	status = dns_cache_get(T_PTR, ipstr, &hbuf, 1, NULL);
 	if (status == mf_success) {
 		debug2(80, "%s resolved to %s (cached value)", ipstr, hbuf);
 		*phbuf = hbuf;
@@ -149,7 +156,7 @@ resolve_hostname(const char *host, char **pipbuf)
 	if (!answer)
 		answer = malloc(MAXPACKET);
 	debug1(80,"Getting IP address for %s", host);
-	status = dns_cache_get(T_A, host, &ipbuf, 1);
+	status = dns_cache_get(T_A, host, &ipbuf, 1, NULL);
 	if (status == mf_success) {
 		debug2(80, "%s resolved to %s (cached value)", host, ipbuf);
 		*pipbuf = ipbuf;
diff --git a/mfd/dns.h b/mfd/dns.h
index 9ded5cef..bca7f684 100644
--- a/mfd/dns.h
+++ b/mfd/dns.h
@@ -29,8 +29,17 @@ typedef enum {
 #endif 
 
 #define MAXMXCOUNT 32
-typedef char *mxbuf_t[MAXMXCOUNT];
 
+#define MXF_MAX   0x01
+#define MXF_REUSE 0x02
+
+struct mxbuf {
+	int mx_flags;
+	size_t mx_max;
+	char **mx_buf;
+	size_t mx_cnt;
+};
+	
 #define MAXCNAMEDEPTH 24 /* FIXME */
 
 #ifdef HAVE_PTHREAD
@@ -66,10 +75,12 @@ typedef char *mxbuf_t[MAXMXCOUNT];
 
 #define UPDATE_TTL(m, ttl) do { if ((m) > (ttl)) (m) = (ttl); } while(0)
 
+void mxbuf_init(struct mxbuf *mxbuf);
+void mxbuf_free(struct mxbuf *mxbuf);
+
 int dns_str_is_ipv4(const char *addr);
-dns_status dns_get_mx_records(const char *host, int maxdepth, mxbuf_t mxbuf,
-			      size_t *mxcount, unsigned long *ttl);
-void dns_freemx(mxbuf_t mxbuf);
+dns_status dns_get_mx_records(const char *host, int maxdepth,
+			      struct mxbuf *mxbuf, unsigned long *ttl);
 
 int dns_reverse_ipstr(const char *ipstr, char *revipstr);
 
diff --git a/mfd/dnsbase.c b/mfd/dnsbase.c
index b2b3087b..c3f985c3 100644
--- a/mfd/dnsbase.c
+++ b/mfd/dnsbase.c
@@ -56,7 +56,7 @@ comp_pref(const void *a, const void *b)
    
 static dns_status
 _getmx(const char *host, unsigned char *answer, size_t answer_size,
-       mxbuf_t mxbuf, size_t *pcount, unsigned long *pttl)
+       struct mxbuf *mxbuf, unsigned long *pttl)
 {
 	int i, n, nmx;
 	struct mx_buffer mx_buffer[MAXMXCOUNT];
@@ -138,7 +138,7 @@ _getmx(const char *host, unsigned char *answer, size_t answer_size,
 		mx_buffer[nmx].name = strdup(tname);
 		debug2(20,"MX %u %s", mx_buffer[nmx].pref,
 			   mx_buffer[nmx].name);
-		if (++nmx >= MAXMXCOUNT)
+		if (++nmx >= mxbuf->mx_max)
 			break;
 	}
 
@@ -146,10 +146,10 @@ _getmx(const char *host, unsigned char *answer, size_t answer_size,
 	qsort(mx_buffer, nmx, sizeof mx_buffer[0], comp_pref);
 
 	/* Prepare return value */
-	memset(mxbuf, 0, sizeof(mxbuf_t));
+	mxbuf_init(mxbuf);
 	for (i = 0; i < nmx; i++) 
-		mxbuf[i] = mx_buffer[i].name;
-	*pcount = nmx;
+		mxbuf->mx_buf[i] = mx_buffer[i].name;
+	mxbuf->mx_cnt = nmx;
 	return dns_success;
 }
 
@@ -181,8 +181,8 @@ MUTEX_DCL(dns_mutex)
    to its parent domains until any record is found or recursion depth reaches
    MAXDEPTH */
 dns_status
-dns_get_mx_records(const char *host, int maxdepth, mxbuf_t mxbuf,
-		   size_t *mxcount, unsigned long *ttl)
+dns_get_mx_records(const char *host, int maxdepth, struct mxbuf *mxbuf,
+		   unsigned long *ttl)
 {
 	char *hbuf = NULL;
 	dns_status status = dns_failure;
@@ -207,7 +207,7 @@ dns_get_mx_records(const char *host, int maxdepth, mxbuf_t mxbuf,
 				if (ttl)
 					*ttl = ~(unsigned long)0;
 				status = _getmx(p, answer, MAXPACKET, mxbuf,
-						mxcount, ttl);
+						ttl);
 				if (status == dns_success 
 				    || status == dns_temp_failure)
 					break;
@@ -224,11 +224,35 @@ dns_get_mx_records(const char *host, int maxdepth, mxbuf_t mxbuf,
 }
 
 void
-dns_freemx(mxbuf_t mxbuf)
+mxbuf_init(struct mxbuf *mxbuf)
 {
-	int i;
-	for (i = 0; i < MAXMXCOUNT && mxbuf[i]; i++)
-		free(mxbuf[i]);
+	if (!(mxbuf->mx_flags & MXF_MAX))
+		mxbuf->mx_max = MAXMXCOUNT;
+	if (mxbuf->mx_flags & MXF_REUSE) {
+		int i;
+		
+		for (i = 0; i < mxbuf->mx_max && mxbuf->mx_buf[i]; i++) {
+			free(mxbuf->mx_buf[i]);
+			mxbuf->mx_buf[i] = NULL;
+		}
+	} else {
+		mxbuf->mx_buf = xcalloc(mxbuf->mx_max,
+					sizeof(mxbuf->mx_buf[0]));
+		mxbuf->mx_flags |= MXF_REUSE;
+	}
+	mxbuf->mx_cnt = 0;
+}
+
+void
+mxbuf_free(struct mxbuf *mxbuf)
+{
+	if (mxbuf->mx_flags & MXF_REUSE) {
+		int i;
+
+		for (i = 0; i < mxbuf->mx_max && mxbuf->mx_buf[i]; i++)
+			free(mxbuf->mx_buf[i]);
+		mxbuf->mx_buf = NULL;
+	}
 }
 
 #define LOOKUP_FAILURE  -1
diff --git a/mfd/dnscache.c b/mfd/dnscache.c
index ff1a1c25..47c72684 100644
--- a/mfd/dnscache.c
+++ b/mfd/dnscache.c
@@ -32,7 +32,7 @@
 
 static mf_status
 parse_value(int qtype, const char *keystr,
-	    int argc, char **argv, char **rbuf, size_t rcnt)
+	    int argc, char **argv, char **rbuf, size_t rcnt, size_t *pcnt)
 {
 	size_t i;
 	char *p;
@@ -56,6 +56,8 @@ parse_value(int qtype, const char *keystr,
 		rbuf[i] = argv[i + 1];
 		argv[i + 1] = NULL;
 	}
+	if (pcnt)
+		*pcnt = i;
 	for (; i < rcnt; i++) 
 		rbuf[i] = NULL;
 	return mf_success;
@@ -101,7 +103,8 @@ dns_free_key(DBM_DATUM *key)
 }
 
 mf_status
-dns_cache_get(int type, const char *keystr, char **rbuf, size_t rcnt)
+dns_cache_get(int type, const char *keystr, char **rbuf, size_t rcnt,
+	      size_t *pcnt)
 {
 	mf_status rc;
 	DBM_FILE db;
@@ -140,7 +143,8 @@ dns_cache_get(int type, const char *keystr, char **rbuf, size_t rcnt)
 			       mu_strerror(rc));
 			rc = mf_failure;
 		} else
-			rc = parse_value(type, keystr, argc, argv, rbuf, rcnt);
+			rc = parse_value(type, keystr, argc, argv, rbuf, rcnt,
+					 pcnt);
 		mu_argcv_free(argc, argv);
 		mu_dbm_datum_free(&contents);
 	} else {
diff --git a/mfd/mailfromd.h b/mfd/mailfromd.h
index 648a57d7..e3adbffe 100644
--- a/mfd/mailfromd.h
+++ b/mfd/mailfromd.h
@@ -150,8 +150,8 @@ mf_status resolve_ipstr_domain(const char *ipstr, const char *domain,
 			       char **phbuf);
 mf_status resolve_hostname(const char *host, char **pipbuf);
 	
-mf_status getmx(const char *ipstr, mxbuf_t mxbuf);
-mf_status getmxip(char *host, GACOPYZ_UINT32_T ipbuf[MAXMXCOUNT],
+mf_status getmx(const char *ipstr, struct mxbuf *mxbuf);
+mf_status getmxip(char *host, GACOPYZ_UINT32_T *ipbuf, size_t ipmax,
 		  size_t *pcount);
 
 
@@ -244,6 +244,9 @@ enum stack_expand_policy {
 };
 extern enum stack_expand_policy stack_expand_policy;
 
+extern size_t max_callout_mx;
+extern size_t max_match_mx;
+
 
 /* Filter script parser */
 
@@ -1054,7 +1057,7 @@ mf_status cache_get2(const char *email, const char *client_addr);
 void cache_insert2(const char *email, const char *client_addr, mf_status rc);
 
 mf_status dns_cache_get(int type, const char *keystr, char **rbuf,
-			size_t rcnt);
+			size_t rcnt, size_t *pcnt);
 void dns_cache_put(int type, const char *keystr, time_t ttl, char **rbuf,
 		   size_t rcnt);
 
diff --git a/mfd/main.c b/mfd/main.c
index 1211965a..4a6bbba5 100644
--- a/mfd/main.c
+++ b/mfd/main.c
@@ -111,6 +111,9 @@ int stack_trace_option;          /* Print stack traces on runtime errors */
 char *file_option;               /* File name for DB management commands */
 struct db_format *format_option;
 
+size_t max_callout_mx = MAXMXCOUNT;
+size_t max_match_mx = MAXMXCOUNT;
+
 /* Timeouts */
 time_t smtp_timeout_soft[SMTP_NUM_TIMEOUT] = {
 	10,
@@ -2299,12 +2302,19 @@ struct mu_cfg_param mf_cfg_param[] = {
 
 	{ "database", mu_cfg_section, NULL },
 
+	{ "max-callout-mx", mu_cfg_size, &max_callout_mx, 0, NULL,
+	  N_("Maximum number of MXs to be polled during "
+	     "callout verification.") },
+	
 	{ "callout-url", mu_cfg_callback,
 	  NULL, 0,
 	  cb_callout_url,
 	  N_("URL of the callout server"),
 	  N_("url") },
 
+	{ "max-match-mx", mu_cfg_size, &max_match_mx, 0, NULL,
+	  N_("Maximum number of MXs used by MFL \"mx match\" operation.") },
+
 	{ "runtime", mu_cfg_section, NULL },
 	
 	{ NULL }
diff --git a/mfd/prog.c b/mfd/prog.c
index 07645b43..f1b2a6c2 100644
--- a/mfd/prog.c
+++ b/mfd/prog.c
@@ -1391,7 +1391,7 @@ mx_match(eval_environ_t env, char *string,
 	 int (*matcher)(const char *name, void *data), void *data)
 {
 	int rc = 0;
-	mxbuf_t mxbuf;
+	struct mxbuf mxbuf;
 	mf_status mxstat;
 
 	char *p = strchr(string, '@');
@@ -1399,19 +1399,23 @@ mx_match(eval_environ_t env, char *string,
 		p++;
 	else
 		p = string;
-	mxstat = getmx(p, mxbuf);
+	mxbuf.mx_max = max_match_mx;
+	mxbuf.mx_flags = MXF_MAX;
+	mxstat = getmx(p, &mxbuf);
 	rc = 0;
 	if (mxstat == mf_success) {
 		int i;
 		
-		for (i = 0; i < MAXMXCOUNT && mxbuf[i]; i++) {
-			if (matcher(mxbuf[i], data)) {
+		for (i = 0; i < mxbuf.mx_cnt; i++) {
+			if (matcher(mxbuf.mx_buf[i], data)) {
 				rc = 1;
 				break;
 			}
 		}
-		dns_freemx(mxbuf);
-	} else if (mxstat != mf_not_found)
+	}
+	mxbuf_free(&mxbuf);
+
+	if (!mf_resolved(mxstat))
 		env_throw(env, mxstat, "cannot get MXs for %s", p);
 	return rc;
 }
diff --git a/mfd/spf.c b/mfd/spf.c
index 03e431a0..5ff30091 100644
--- a/mfd/spf.c
+++ b/mfd/spf.c
@@ -643,8 +643,8 @@ static spf_term_result
 mech_mx(spf_data *dat, spf_term_arg *arg, unsigned long masklen)
 {
 	unsigned long netmask = make_netmask(masklen);
-	mxbuf_t mxbuf;
-	size_t i, mxcount;
+	struct mxbuf mxbuf;
+	size_t i;
 	spf_term_result result = spf_term_nomatch;
 	const char *domain_spec;
 	unsigned long ttl;
@@ -657,18 +657,17 @@ mech_mx(spf_data *dat, spf_term_arg *arg, unsigned long masklen)
 	debug2(2, "MX domain_spec=%s, netmask=%x",
 	       domain_spec, netmask);
 
-	DNS_CATCH(dns_get_mx_records(domain_spec, 1, mxbuf, &mxcount, &ttl));
+	mxbuf.mx_flags = MXF_MAX;
+	mxbuf.mx_max = 10;
+	DNS_CATCH(dns_get_mx_records(domain_spec, 1, &mxbuf, &ttl));
 	UPDATE_TTL(dat->ttl, ttl);
 	
-	if (mxcount > 10)
-		mxcount = 10;
-
-	for (i = 0; i < mxcount; i++) {
+	for (i = 0; i < mxbuf.mx_cnt; i++) {
 		spf_term_arg targ;
 		spf_term_result res;
 		
 		targ.type = spf_arg_domain_spec;
-		targ.v.domain_spec = mxbuf[i];
+		targ.v.domain_spec = mxbuf.mx_buf[i];
 		res = mech_a(dat, &targ, masklen);
 		if (res == spf_term_match) {
 			result = res;
@@ -676,7 +675,7 @@ mech_mx(spf_data *dat, spf_term_arg *arg, unsigned long masklen)
 		}
 	}
 
-	dns_freemx(mxbuf);
+	mxbuf_free(&mxbuf);
 	return result;
 }