I think we all have seen this countless times.
So how about the moderators have a way to add links to a filter, and any link to a database/table that will automatically stop messages with that link from being sent. Then when someone tries to send it, it will say it was successful sending it, but don’t actually send it.
I also recommend Roblox sending an email to the hosting service for the website being spammed. Since they could get millions of records of the same message as proof of abuse.