diff --git a/data/conf/dovecot/sieve_after b/data/conf/dovecot/sieve_after
index d668a94c..0b43dbcf 100644
--- a/data/conf/dovecot/sieve_after
+++ b/data/conf/dovecot/sieve_after
@@ -7,6 +7,18 @@ require "envelope";
 if header :contains "X-Spam-Flag" "YES" {
   fileinto "Junk";
 }
-if allof (envelope :detail :matches "to" "*", header :contains "X-Moo-Tag" "YES") {
-  fileinto :create "INBOX/${1}";
+
+if allof (
+  envelope :detail :matches "to" "*",
+  header :contains "X-Moo-Tag" "YES",
+  mailboxexists "INBOX/${s}"
+  ) {
+    fileinto "INBOX/${s}";
+}
+elsif allof (
+  envelope :detail :matches "to" "*",
+  header :contains "X-Moo-Tag" "YES"
+  ) {
+    set :lower "s" "${1}";
+    fileinto :create "INBOX/${s}";
 }