Setup inbound message processing Create a user with a working email address and send them an email Confirm that the Return-Path / noreply email has been overridden with a custom VERP email Create a user with a broken email address and confirm them manually (Real life use cases are: a user has changed email address, the inbox is full, the email host has gone away etc) Send an email to them and wait for the bounce to come back (ie watch the VERP mailbox) Run the pickup cron task and you should see something like this: Found 1 messages to parse. Parsing... - Parsing message 19 -- Subject: Undelivered Mail Returned to Sender -- From: MAILER-DAEMON@smtp.catalyst-au.net -- Recipient: moodle+AAAAAAAAAAQAAAAAAAA4RgAAAAA/mjZ/PA5UCaeWW2gZoQCQ@moodle.catalyst-au.net -- Processing the message as user 14406 (teacher). -- Validation completed. Fetching rest of message content. --> Passing to Inbound Message handler \tool_messageinbound\message\inbound\bounce_handler === Increment bounce count to 1 for breefwrwndan+willrogers@catalyst-au.net === Repeat the above, but between sending the email and running the pickup task change the users email to something else (could be valid or not) and then run the pickup and confirm you see something like this: Found 1 messages to parse. Parsing... - Parsing message 20 -- Subject: Undelivered Mail Returned to Sender -- From: MAILER-DAEMON@smtp.catalyst-au.net -- Recipient: moodle+AAAAAAAAAAQAAAAAAAA4RgAAAAA/mjZ/PA5UCaeWW2gZoQCQ@moodle.catalyst-au.net -- Processing the message as user 14406 (teacher). -- Validation completed. Fetching rest of message content. --> Passing to Inbound Message handler \tool_messageinbound\message\inbound\bounce_handler === Bounce message ignored because users email has changed since sent. ===