[stephenr]

> when I give out my email address, the receiver can give my address to a third party

Use sub-addressing [1]

So, if you signup on example.com, and your email is "[e-mail]" you give them "[e-mail]" or whatever format works for your mailbox provider/software.

If you wanted to go one step further, a filter could be configured to look at the sub-address component, and compare it with the sender's domain and mark it as spam if there isn't a match.

1. https://en.wikipedia.org/wiki/Email_address#Sub-addressing

[clusmore]

This can work for online services during signup. I haven't yet seen this, but I wouldn't be surprised if some services were smart enough to drop the sub-address before on-selling your email.

In face-to-face exchanges (for me recently, this came up a lot while giving out my address to real estate agents), anything involving '+' causes a huge amount of confusion and they start asking questions. I'd much rather a "normal" looking address, where I'm perfectly happy for normal to be say base64 with '.', '_' and '-' and as the three special characters (at least people will think its valid).

[stephenr]

+ doesn't have to be the separator. Gmail supports a '.' for example, and if you run the mail server yourself, its just limited by what characters the software you run supports.

If you have your own domain, you can of course also do [e-mail] and have it go to a catch-all style mailbox.