This a reasonably priced paid service that does already exist, it's not from Google and no, I won't name it neither publicly nor privately because I used it for years and I don't want their domain to be banned by those requiring your email address for everything. If you know how to search you will probably find it. Basically you sign with them using one valid email address, then on their interface you can create as many addresses as you need (IIRC there is a limit but I used even dozens at a time without problems) and add a keyword to them. All of those addresses will be redirected to the email you signed with, but the From: field will also contain the keyword you specified so that if you create an address for each service you sign up for, you instantly recognize who is spamming you when they use that address. This is very effective and I filtered out a lot of spammers. I'm surprised there are no more services like this one around, or probably there are many but they keep a low profile to avoid being banned. That's why I'm not going to name that service, sorry. But it does exist indeed and is technically easy to implement.