diff --git src/file.c src/file.c
index cdfa67f..d35d187 100644
--- src/file.c
+++ src/file.c
@@ -655,7 +655,7 @@ char *message_name (struct emailinfo *email)
   else
     {
 #endif /* HAVE_LIBFNV */
-      sprintf (buffer, "%.4d", email->msgnum);
+      sprintf (buffer, set_message_pattern ? set_message_pattern : "%.4d" , email->msgnum);
       return buffer;
 #ifdef HAVE_LIBFNV
     }
diff --git src/setup.c src/setup.c
index 3735391..0289a20 100644
--- src/setup.c
+++ src/setup.c
@@ -146,6 +146,7 @@ char *set_mhtmlfooter;
 char *set_attachmentlink;
 char *set_unsafe_chars;
 char *set_filename_base;
+char *set_message_pattern;
 
 char *set_folder_by_date;
 char *set_latest_folder;
@@ -910,6 +911,9 @@ struct Config cfg[] = {
      "# option is set to plus a file name extension if one can be found\n"
      "# in the name supplied by the message. This option is mainly for\n"
      "# languages that use different character sets from English.\n", FALSE},
+    {"message_pattern", &set_message_pattern, NULL, CFG_STRING,
+     "# This option overrides the default pattern \"%.4d\" for creating\n"
+     "# html files.\n", FALSE},
 };
 
 /* ---------------------------------------------------------------- */
diff --git src/setup.h src/setup.h
index 3a57a26..7f944c0 100644
--- src/setup.h
+++ src/setup.h
@@ -162,6 +162,7 @@ extern char *set_mhtmlfooter;
 extern char *set_attachmentlink;
 extern char *set_unsafe_chars;
 extern char *set_filename_base;
+extern char *set_message_pattern;
 extern bool set_linkquotes;
 
 extern char *set_antispamdomain;