diff --git a/cyrus-imapd-2.3.15-nodebug.patch b/cyrus-imapd-2.3.15-nodebug.patch
new file mode 100644
index 0000000..d91c6a2
--- /dev/null
+++ b/cyrus-imapd-2.3.15-nodebug.patch
@@ -0,0 +1,73 @@
+diff -up cyrus-imapd-2.3.15/lib/prot.c.nodebug cyrus-imapd-2.3.15/lib/prot.c
+--- cyrus-imapd-2.3.15/lib/prot.c.nodebug	2009-11-05 14:20:53.845020152 +0100
++++ cyrus-imapd-2.3.15/lib/prot.c	2009-11-05 14:21:35.932145246 +0100
+@@ -329,7 +329,7 @@ static int is_incompressible(const char 
+ 
+     while (sig->type) {
+ 	if (n >= sig->len && !memcmp(p, sig->sig, sig->len)) {
+-	    syslog(LOG_DEBUG, "data is %s", sig->type);
++// 	    syslog(LOG_DEBUG, "data is %s", sig->type);
+ 	    return 1;
+ 	}
+ 	sig++;
+@@ -642,14 +642,14 @@ int prot_fill(struct protstream *s)
+ 	    s->zstrm->next_out = s->zbuf;
+ 	    s->zstrm->avail_out = s->zbuf_size;
+ 
+-	    syslog(LOG_DEBUG, "inflate(%d bytes)", s->cnt);
++// 	    syslog(LOG_DEBUG, "inflate(%d bytes)", s->cnt);
+ 
+ 	    do {
+ 		if (!s->zstrm->avail_out) {
+ 		    /* Need more space to decompress */
+-		    syslog(LOG_DEBUG,
+-			   "growing decompress buffer from %d to %d bytes",
+-			   s->zbuf_size, s->zbuf_size + PROT_BUFSIZE);
++// 		    syslog(LOG_DEBUG,
++// 			   "growing decompress buffer from %d to %d bytes",
++// 			   s->zbuf_size, s->zbuf_size + PROT_BUFSIZE);
+ 
+ 		    s->zbuf = (unsigned char *)
+ 			xrealloc(s->zbuf, s->zbuf_size + PROT_BUFSIZE);
+@@ -670,7 +670,7 @@ int prot_fill(struct protstream *s)
+ 	    s->ptr = s->zbuf;
+ 	    s->cnt = s->zbuf_size - s->zstrm->avail_out;
+ 
+-	    syslog(LOG_DEBUG, "   => decompressed to %d bytes", s->cnt);
++// 	    syslog(LOG_DEBUG, "   => decompressed to %d bytes", s->cnt);
+ 	}
+ #endif /* HAVE_ZLIB */
+ 	
+@@ -760,8 +760,8 @@ static int prot_flush_encode(struct prot
+ 	     * Oversize the buffer, so we (hopefully) eliminate
+ 	     * multiple small incremental reallocations.
+ 	     */
+-	    syslog(LOG_DEBUG, "growing compress buffer from %u to %lu bytes",
+-		   s->zbuf_size, def_size + PROT_BUFSIZE);
++// 	    syslog(LOG_DEBUG, "growing compress buffer from %u to %lu bytes",
++// 		   s->zbuf_size, def_size + PROT_BUFSIZE);
+ 
+ 	    s->zbuf_size = def_size + PROT_BUFSIZE;
+ 	    s->zbuf = (unsigned char *) xrealloc(s->zbuf, s->zbuf_size);
+@@ -772,9 +772,9 @@ static int prot_flush_encode(struct prot
+ 	s->zstrm->next_out = s->zbuf;
+ 	s->zstrm->avail_out = s->zbuf_size;
+ 
+-	syslog(LOG_DEBUG, "deflate(%d bytes, level=%d, flush=%s)",
+-	       left, s->zlevel,
+-	       zflush == Z_FULL_FLUSH ? "FULL" : "SYNC");
++// 	syslog(LOG_DEBUG, "deflate(%d bytes, level=%d, flush=%s)",
++// 	       left, s->zlevel,
++// 	       zflush == Z_FULL_FLUSH ? "FULL" : "SYNC");
+ 
+ 	if (s->boundary) {
+ 	    /* Set (new) compression level */
+@@ -791,7 +791,7 @@ static int prot_flush_encode(struct prot
+ 	ptr = s->zbuf;
+ 	left = s->zbuf_size - s->zstrm->avail_out;
+ 
+-	syslog(LOG_DEBUG, "   => compressed to %d bytes", left);
++// 	syslog(LOG_DEBUG, "   => compressed to %d bytes", left);
+     }
+ #endif /* HAVE_ZLIB */
+ 
diff --git a/cyrus-imapd.spec b/cyrus-imapd.spec
index ebe9e46..ffaf39a 100644
--- a/cyrus-imapd.spec
+++ b/cyrus-imapd.spec
@@ -1,6 +1,6 @@
 Name: cyrus-imapd
 Version: 2.3.15
-Release: 3%{?dist}
+Release: 4%{?dist}
 
 # ********************** BUILD TIME OPTIONS START **********************
 
@@ -116,6 +116,10 @@ Patch18: cyrus-imapd-2.3.7-krb4.patch
 # https://bugzilla.redhat.com/show_bug.cgi?id=461875
 Patch19: cyrus-imapd-2.3.12p2-current-db.patch
 Patch20: cyrus-imapd-2.3.15-bufov.patch
+
+# required for c-i <= 2.3.15, rhbz#528093
+Patch21: cyrus-imapd-2.3.15-nodebug.patch
+
 BuildRoot: %(mktemp -ud %{_tmppath}/%{name}-%{version}-%{release}-XXXXXX)
 BuildRequires: autoconf >= 2.59
 BuildRequires: cyrus-sasl-devel >= 2.1.15-1, perl-devel, tcp_wrappers
@@ -214,6 +218,7 @@ one running the server.
 %patch18 -p1 -b .krb4
 %patch19 -p1 -b .db4.7
 %patch20 -p1 -b .bufov
+%patch21 -p1 -b .nodebug
 
 # only to update config.* files
 automake -a -f -c || :
@@ -731,6 +736,9 @@ fi
 %{_mandir}/man1/*
 
 %changelog
+* Thu Nov 05 2009 Michal Hlavinka <mhlavink@redhat.com> - 2.3.15-4
+- do not fill logs with mail (de)compression messages (#528093)
+
 * Fri Oct 09 2009 Michal Hlavinka <mhlavink@redhat.com> - 2.3.15-3
 - fix cyrus user shell for db import (#528126)