There are two common reasons that a "missed spam" report is returned as "undeliverable" and the accompanying error message will normally indicate which one is the problem.

Recipient address not found

If the bounce error indicates that the recipient address is invalid, this usually means the MX records for your domain are not configured correctly. This also means that your mail (or most of it) is not being filtered by our system.

• Why does this happen?:
  All users are assigned a unique address for reporting their missed spam. When a missed spam report arrives, it is forwarded to a hidden system address on your domain. This is done to ensure that the report is processed by the same filtering servers that handled the original spam message. However, when the MX records for your domain are configured wrong, the forwarded message ends up being routed back to your own mail server instead of reaching the internal address on our filtering host.
• Solution: Update your domain to use the assigned MX records. Refer to the Service setup and diagnostics area of the control panel.

 

Message rejected as spam

If you receive a bounce back saying that the message was rejected as spam, this means that your mail server has blocked you from sending the message because they identified it as spam.

• Why did my mail server catch this when SpamHero didn't?
  It may seem strange that our filters missed a message that your mail server is correctly identifying as "spam". The biggest key is the amount of time that passed from the time the message arrived to the time you're reporting it as "missed spam". Your mail server accepted it for delivery to your mailbox but is rejecting it as a forwarded message, which means that new rules were created to adapt to the latest spam campaigns. Or your mail server may have very aggressive anti-spam rules for outbound mail (which may be prone to block clean mail too).
• Solution: When processing "missed spam" reports, our system only needs to see the original header details (From, To, Date and Subject) to properly match the message to the original copy. So you can remove the message body when forwarding the spam sample and that will usually be enough for your mail provider to let the message through.
   
  Example missed spam report - with the original headers and the message body removed
  

  ------ Forwarded Message ------
  From: "Global Prize Notifications" <winners@prizenotify.net>
  To: "Johnathan Q. Public" <johnathan.public@example.com>
  Date: 02/09/2024 2:14:45 PM
  Subject: Congratulations! Confirm Your Prize Now!
  
  (Message body removed)

  There's no need to indicate that the message body was removed, that was just there to illustrate.