Grey Listing
Although Grey Listing was originally built as a tool to block email robots, it can also work as an awesome tool used to block UCE. It works by temporarily bounces a message destined to your users. Once the message is "bounced" temporarily, the address and host are noted on the list. Once the time is up, the message is resent and this time accepted by your mail server. Most programs do not attempt to retry sending a message. Those programs will no longer be able to send email directly to your server without a MTA (Message Transfer Agent).
Grey listing is an attempt to allow legitimate people to receive E-Mail in a safe manner. It works by writing the email addresses and hostname to a database and sending a temporary bounce message back to the remote MTA. The remote MTA will then cache the message and retry after the appointed time. Once the time expires, the entry on the database allows the email to come in.
Grey Listing is enabled by installing the add-on onto your server (Even if the server is forwarding):
- Install a Database package of your choice.
- Now enable this package on your server.
- Install a Grey Listing package of your choice.
- Now enable this package on your server.
- Test your installation
More information
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