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*
That ship has sailed, but you have to sign up with a mail account that offers throw away addresses (like yahoo! mail or others). They just put the mails from all throwaways also into you main mailbox. If later you can’t ubsubscribe, you can just delete the throwaway. Only problem is, for replies you have to use the mail providers way (i.e. webmailer) so your client doesn’t reply with your main address. But I found it very rare I reply to mails from subscriptions.
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.