diff -Naur cyrus-imapd-2.2.6/imap/lmtp_sieve.c cyrus-imapd-2.2.6.autosieve.uncompiled/imap/lmtp_sieve.c
--- cyrus-imapd-2.2.6/imap/lmtp_sieve.c	2004-06-01 16:47:16.000000000 +0300
+++ cyrus-imapd-2.2.6.autosieve.uncompiled/imap/lmtp_sieve.c	2004-06-20 14:31:59.000000000 +0300
@@ -72,6 +72,8 @@
 #include "util.h"
 #include "version.h"
 #include "xmalloc.h"
+#include "imap_err.h"
+
 
 static int sieve_usehomedir = 0;
 static const char *sieve_dir = NULL;
@@ -98,6 +100,9 @@
 			   int quotaoverride,
 			   int acloverride);
 
+static int autosieve_subfolder(char *userid, struct auth_state *auth_state,
+                               char *subfolder);
+
 static char *make_sieve_db(const char *user)
 {
     static char buf[MAX_MAILBOX_PATH+1];
@@ -312,6 +317,7 @@
 }
 
 
+
 static int sieve_redirect(void *ac, 
 			  void *ic __attribute__((unused)), 
 			  void *sc, void *mc, const char **errmsg)
@@ -444,7 +450,18 @@
 			      sd->username, mdata->notifyheader,
 			      namebuf, quotaoverride, 0);
     }
-
+    if (ret == IMAP_MAILBOX_NONEXISTENT) {
+        /* if "plus" folder under INBOX, then try to create it */
+      syslog(LOG_DEBUG, "calling autosieve folder for : %s", namebuf);
+        ret = autosieve_subfolder(sd->username, sd->authstate, namebuf);
+
+        if (!ret)
+            ret = deliver_mailbox(md->data, mdata->stage, md->size,
+                                  fc->imapflags->flag, fc->imapflags->nflags,
+                                  (char *) sd->username, sd->authstate, md->id,
+                                  sd->username, mdata->notifyheader,
+                                  namebuf, quotaoverride, 0);
+    }
     if (!ret) {
 	snmp_increment(SIEVE_FILEINTO, 1);
 	return SIEVE_OK;
@@ -882,3 +899,111 @@
 
     return r;
 }
+
+
+#define SEP '|'
+
+static int autosieve_subfolder(char *userid, struct auth_state *auth_state,
+                               char *subfolder)
+{
+     char foldername[MAX_MAILBOX_NAME+1];
+     char f[MAX_MAILBOX_NAME+1];
+     char nam[MAX_MAILBOX_NAME+1];
+     const char *subf ;
+     char *checkfoldername, *user;
+     char *p, *q, *next_subf, *mbox;
+     int len, r = 0;
+     int createsievefolder = 0;
+
+    /* Check if subfolder is NULL */
+    if(subfolder == NULL)
+       return IMAP_MAILBOX_NONEXISTENT;
+
+    strlcpy(foldername, subfolder,strlen(subfolder)+1);
+
+    if(config_virtdomains && (p = strrchr(userid,'@')) ) {
+        user = xmalloc((p - userid +1)*sizeof(char));
+        strlcpy(user,userid,(p - userid +1));
+    }
+    else
+        user = userid;
+
+
+
+    strlcpy(nam,"user.",6);
+    strlcat(nam,user,MAX_MAILBOX_NAME);
+    strlcat(nam,".",MAX_MAILBOX_NAME);
+
+
+    if(!(checkfoldername = strchr(foldername,(int)'!')))
+        checkfoldername = foldername;
+    else
+        checkfoldername++;
+    if(strchr((checkfoldername + strlen(nam) +1),'.'))  { //we are in internal namespace
+        return IMAP_MAILBOX_BADNAME;
+     }
+
+    if(user != userid)
+        free(user);
+
+
+    if (config_getswitch(IMAPOPT_ANYSIEVEFOLDER))
+        createsievefolder = 1;
+    else if ((subf = config_getstring(IMAPOPT_AUTOSIEVEFOLDERS)) != NULL) {
+             /*
+              * mbox contains only the subfolder to be created name
+              */
+              if((mbox = strrchr(foldername, (int) '.'))) // We are in internal namespace. Megalh efeyresh to internal namespace :))
+                mbox++;
+              else
+                return IMAP_MAILBOX_BADNAME; //Probably we have a BAD combination of sieve filter and imap.conf
+
+              /* Roll through subf */
+              next_subf = (char *) subf;
+              while (*next_subf) {
+                    for (p = next_subf ; isspace((int) *p) || *p == SEP ; p++);
+                    for (next_subf = p ; *next_subf && *next_subf != SEP ; next_subf++);
+                    for (q = next_subf ; q > p && (isspace((int) *q) || *q == SEP || !*q); q--);
+
+                    if (!*p) continue;
+                    /*
+                     * This is a preliminary length check based on the assumption
+                     * that the *final* internal format will be something
+                     * like user.userid.subfolder(s).
+                     */
+                    len = q - p + 1;
+
+                    if (len  > sizeof(f) - strlen(userid) - 5)
+                        r = IMAP_MAILBOX_BADNAME;
+
+                    if (!r) {
+                        strncpy(f, p, len);
+                        f[len] = '\0';
+
+                        if (!strcmp(f, mbox)) {
+                            createsievefolder = 1;
+                            break;
+                        }
+                    }
+              }
+         }
+
+    if (createsievefolder) {
+
+// Folder is already in internal namespace format
+        r = mboxlist_createmailbox(foldername, MAILBOX_FORMAT_NORMAL, NULL,
+                                           1, userid, auth_state, 0, 0, 0);
+        if (!r) {
+            mboxlist_changesub(foldername, userid, auth_state, 1, 1);
+            syslog(LOG_DEBUG, "Ondemand subfolder: User %s, subfolder %s creation succeeded.",
+                                                   userid, foldername);
+            return 0;
+        } else {
+            syslog(LOG_ERR, "Requested subfolder: User %s, subfolder %s creation failed. %s",
+                                                  userid, foldername,error_message(r));
+            return r;
+        }
+    } else
+        return IMAP_MAILBOX_NONEXISTENT;
+}
+
diff -Naur cyrus-imapd-2.2.6/lib/imapoptions cyrus-imapd-2.2.6.autosieve.uncompiled/lib/imapoptions
--- cyrus-imapd-2.2.6/lib/imapoptions	2004-05-25 03:03:05.000000000 +0300
+++ cyrus-imapd-2.2.6.autosieve.uncompiled/lib/imapoptions	2004-06-20 14:31:59.000000000 +0300
@@ -736,6 +736,15 @@
 /* If enabled, lmtpd will look for Sieve scripts in user's home
    directories: ~user/.sieve. */
 
+{ "anysievefolder", 0, SWITCH }
+/* It must be "yes" in order to permit the autocreation of any INBOX subfolder 
+   requested by a sieve filter, through the "fileinto" action. (default = no) */
+
+{ "autosievefolders", NULL, STRING }
+/* It is a "|" separated list of subfolders of INBOX that will be automatically created, 
+   if requested by a sieve filter, through the "fileinto" action. (default = null)
+   i.e. autosievefolders: Junk | Spam */
+
 { "singleinstancestore", 1, SWITCH }
 /* If enabled, lmtpd and nntpd attempt to only write one copy of a message per
    partition and create hard links, resulting in a potentially large