Emails to request from unknown contacts can be posted to ticket
Take two contacts A and B belonging to different accounts. (request == ticket)
Customer A creates ticket [##1234##]
Customer B creates a different ticket [##1111##]
Customer B sends an email response but accidently uses [##1234##]. This message is posted on the ticket [##1234##].
Ideally, the portal would have the option to block, bounce, or post the message internally. This will likely need to fit into the use cases where 1) another user from Customer A emails a response (allow), 2) another account tries to email (block or bounce), or 3) our internal system would like to attach data to the request. I'd imagine this would be something like an authorized sender list. Posting as an internal comment would also work...