I have been thinking about using some sort of UUID-generator ([UUID]@mydomain.xz) whenever I sign up for a new site, but I just can not think of a _good_ way to keep track of them.
If only there were some convenient software for keeping track of your unique login names and passwords for each site you use.
If you mean password manager, sure. But I was thinking of e-mails received, how would I know if the emails came from the "right" sites? Would have to open up a text file, or login to my password manager, just to check. I do not think that is a great way to keep track of it.