Not just the mechanisms above, there's always legal requests by law enforcement.Whilst that's unlikely to be the threat that most folks just wanting to remain genuinely anonymous on the classes of personal site we continually see being breached, it's also an unnecessary risk.Gmail (or equivalent - there are many other free online mail providers) gives you a full blown email address and obviously requests a lot of info in the process.A great alternative where an email address is simply a requirement to entry and you care little about anything that's actually sent to it is to use a Mailinator address.One of those ways is obviously when data is breached from a system and all the email addresses are on easy display: address. It's not always that explicit either, for example Ashley Madison returned slightly different responses which could still be observed. For example, when doing a password reset: If you authenticate to another site using your Gmail account (social logins are increasingly common), then you may be prompted to share data attributes such as your name with that site.
Often people's fabricated personas come undone once payments are involved.
If you're a budding Edward Snowden then you'll need to go much, much further.
Let's jump into it, and we'll start somewhere simple.
For example, you can enter an address such as [email protected] head off to Mailinator, enter the alias and immediately view the contents of the mailbox: There's no authentication and therefore you need to assume there's no confidentiality (although the likelihood of someone stumbling across a genuinely randomised email alias is extremely low), but when email is simply a barrier to site entry then Mailinator is a very simple solution.
Many of the data breaches I come across have numerous Mailinator addresses in them for precisely this reason.