I unsubscribed from a company’s mailing list and then they added me to a new “unsubscribers” list and spammed me again. I then unsubscribed from that list and was added to another “unsubscriber” list. At least this new unsubscriber list was labelled “new”. That makes it so much better. /s*
Many classical email clients have the option to edit the senders address while composing the email. If the mail server does not allow this you usually get an error message on sending.