diff --git a/postfix/.indent.pro b/postfix/.indent.pro
index d5c9972c1..bc5fa9c63 100644
--- a/postfix/.indent.pro
+++ b/postfix/.indent.pro
@@ -257,6 +257,7 @@
 -TXSASL_SERVER
 -TXSASL_SERVER_IMPL
 -TXSASL_SERVER_IMPL_INFO
+-Tcipher_probe
 -Toff_t
 -Tregex_t
 -Tregmatch_t
diff --git a/postfix/HISTORY b/postfix/HISTORY
index 8881cfe7b..5ba0c8253 100644
--- a/postfix/HISTORY
+++ b/postfix/HISTORY
@@ -13149,6 +13149,12 @@ Apologies for any names omitted.
 	all other recipients are in the initial segment).  File:
 	global/rec_types.h.
 
+20070123
+
+	Workaround: OpenSSL falsely concludes that AES256 support
+	is present when only AES128 is available.  Code by Victor
+	Duchovni.  File: tls/tls_misc.c.
+
 Wish list:
 
 	Update message content length when adding/removing headers.
diff --git a/postfix/src/global/mail_version.h b/postfix/src/global/mail_version.h
index 82b46d828..cce3395d8 100644
--- a/postfix/src/global/mail_version.h
+++ b/postfix/src/global/mail_version.h
@@ -20,7 +20,7 @@
   * Patches change both the patchlevel and the release date. Snapshots have no
   * patchlevel; they change the release date only.
   */
-#define MAIL_RELEASE_DATE	"20070122"
+#define MAIL_RELEASE_DATE	"20070123"
 #define MAIL_VERSION_NUMBER	"2.4"
 
 #ifdef SNAPSHOT
diff --git a/postfix/src/tls/Makefile.in b/postfix/src/tls/Makefile.in
index 2c48df724..d3e21510a 100644
--- a/postfix/src/tls/Makefile.in
+++ b/postfix/src/tls/Makefile.in
@@ -151,6 +151,7 @@ tls_mgr.o: ../../include/vstream.h
 tls_mgr.o: ../../include/vstring.h
 tls_mgr.o: tls_mgr.c
 tls_mgr.o: tls_mgr.h
+tls_misc.o: ../../include/argv.h
 tls_misc.o: ../../include/msg.h
 tls_misc.o: ../../include/mymalloc.h
 tls_misc.o: ../../include/name_code.h
diff --git a/postfix/src/tls/tls_misc.c b/postfix/src/tls/tls_misc.c
index f87389819..ac5f25507 100644
--- a/postfix/src/tls/tls_misc.c
+++ b/postfix/src/tls/tls_misc.c
@@ -104,6 +104,7 @@
 #include <mymalloc.h>
 #include <vstring.h>
 #include <stringops.h>
+#include <argv.h>
 
 /* TLS library. */
 
@@ -151,6 +152,41 @@ NAME_CODE tls_cipher_level_table[] = {
     0, TLS_CIPHER_NONE,
 };
 
+typedef struct {
+    char   *algorithm;
+    char   *exclusion;
+} cipher_probe;
+
+static cipher_probe cipher_probe_list[] = {
+
+    /*
+     * Check for missing AES256, OpenSSL only checks for AES128, and then
+     * enables both, because they only have one "is AES" boolean flag in the
+     * cipher property mask. The implementation cannot distinguish between
+     * AES128 and AES256. When some O/S distributions play games with
+     * libcrypto and exclude just the AES256 ciphers, they break the OpenSSL
+     * cipherlist construction code, with clients and servers potentially
+     * negotiating unimplemented ciphers.
+     * 
+     * This problem is peculiar to AES, which is not a single cipher, but a
+     * family of related ciphers. The other OpenSSL symmetric ciphers are
+     * atomic, either implemented or not. We expect that future ciphers will
+     * either also be atomic, or will have one property bit per family member
+     * and will be filtered accurately by OpenSSL.
+     * 
+     * If all else fails, this table can be expanded :-(
+     * 
+     * XXX: the probe for AES256 is enclosed in #ifdef. OpenSSL 0.9.6 and and
+     * earlier don't have AES 256, this requires 0.9.7 or later. We recommend
+     * against use of 0.9.6, it has open issues solved in 0.9.7l and 0.9.8d,
+     * but we are not yet prepared to drop support for 0.9.6.
+     */
+#ifdef SN_aes_256_cbc
+    SN_aes_256_cbc, SSL_TXT_AES "+HIGH",
+#endif
+    0, 0,
+};
+
  /*
   * Parsed OpenSSL version number.
   */
@@ -168,6 +204,9 @@ const char *tls_cipher_list(int cipher_level,...)
 {
     const char *myname = "tls_cipher_list";
     static VSTRING *buf;
+    static ARGV *exclude_unavailable;
+    cipher_probe *probe;
+    int     i;
     va_list ap;
     const char *exclude;
     char   *tok;
@@ -202,6 +241,18 @@ const char *tls_cipher_list(int cipher_level,...)
     if (VSTRING_LEN(buf) == 0)
 	msg_panic("%s: empty cipherlist", myname);
 
+    /*
+     * Exclude ciphers that clueless distributions leave out of libcrypto.
+     */
+    if (exclude_unavailable == 0) {
+	exclude_unavailable = argv_alloc(1);
+	for (probe = cipher_probe_list; probe->algorithm; ++probe)
+	    if (!EVP_get_cipherbyname(probe->algorithm))
+		argv_add(exclude_unavailable, probe->exclusion, (char *) 0);
+    }
+    for (i = 0; i < exclude_unavailable->argc; ++i)
+	vstring_sprintf_append(buf, ":!%s", exclude_unavailable->argv[i]);
+
     va_start(ap, cipher_level);
     while ((exclude = va_arg(ap, char *)) != 0) {
 	if (*exclude == '\0')