Complete Virtual Mail Server/Greylisting

Introduction
Grey-listing is a mixture of white- and black-listing. Previously unknown e-mail addresses are blacklisted and get an error to try again later. A lot of spammers use misbehaving MTA's and thus will not retry. But what if they are a little smarter and do try again? Hopefully by that time, be it an hour or four, the spammer can have been identified as such and be blocked by DNS block or the like. Grey-listing should be concierge very optional. It can bring up issues for users, such as mail taking up to four hours to be delivered. Consider this carefully when deciding to implement grey-listing.

Installation
Grey-listing is actual a policy-daemon for postfix. A package exists for this purpose,. Grey-listing should have been installed already, but if it was not, it can be emerged as usual.

GLD Configuration
A sample configuration file is supplied by gld which will need to be edited and saved as.

GLD will get its own database.

The database gets filled with tables from gld.

After gld is installed and configured it can be started and added to the default runlevel.

Postfix Configuration
Postfix needs to be told to use GLD in. An addition to smptd_recipient_restrictions needs to be made. The option needs to be added. Thus a current smptd_recipient_restrictions should not be changed to match this, only the mentioned part added!

Restarting postfix is all that needs to be done to make it use GLD.

Testing
Send a test message from a domain that is not yet whitelisted (or remove the initial whitelisting) and watch the postfix log for 450 error message.