I'm being harassed regularly by different email addresses sending inappropriate suggestive links to 20 different people including me. Sending stop/unsubscribe/etc. DOES NOT WORK because of the aforementioned change of email address. There is no option to block or report the sender like there is with a phone number.
There should be an option to only receive messages from select numbers and/or addresses to prevent this.
*For standard Messages app came with the phone.*