diff --git a/app/mailboxes/support_mailbox.rb b/app/mailboxes/support_mailbox.rb
index ca7f39a9ab181..94ee9bfdfb36c 100644
--- a/app/mailboxes/support_mailbox.rb
+++ b/app/mailboxes/support_mailbox.rb
@@ -52,8 +52,14 @@ def find_conversation_by_in_reply_to
     @account.conversations.where("additional_attributes->>'in_reply_to' = ?", in_reply_to).first
   end
 
+  BOOKING_CHAT_GROUPING = /(\d+)-.+@mchat.booking.com/
+
   def in_reply_to
-    mail['In-Reply-To'].try(:value)
+    in_reply_to = mail['In-Reply-To'].try(:value)
+    return in_reply_to if in_reply_to
+
+    m = BOOKING_CHAT_GROUPING.match(mail.from)
+    "#{m[1]}@mchat.booking.com" if m
   end
 
   def find_or_create_conversation