| To the initial frustration of some of the senders, he didn't open the packages. |
| One way is to create whitelist email addresses, a special email address that can be given to senders who are not yet whitelisted. |
| These last for about 30 seconds or so, and will ricochet enemy fire right back at their senders. |
| Anti-spam systems also keep blacklists of known spammers, as well as lists of approved senders. |
| It makes it clear that senders cannot send such messages unless they have the recipient's prior consent. |
| This means that many spam senders will never become whitelisted and email will never be accepted from them. |
