On 12/14/19 4:29 PM, Keith Seyffarth wrote:
Grant Taylor via Mailman-Users mailman-users@python.org writes:
On 12/13/19 9:02 PM, Mark Sapiro wrote:
As postgrey learns, it will remember triplets (sender, sending IP, recipient) and not delay them and in addition will whitelist domains that retry successfully more than a few times. The bigger senders are doing things now (more than ever) that they weren't doing 15+ years ago. Now farms of servers will try to contact you. The message may first try from one IP, then from another IP, then from a 3rd.... It may eventually try from the same IP and make it through.
I think most grey list solutions have an option to specify the network (frequently configured a a /24) for the sending IP. This significantly helps with different servers in the same server farm trying to resend messages. Some greylisting solutions also allow you to whitelist a domain or subdomain, but this can result in spammers spoofing that domain getting through...
Keith
Unless you only whitelist domains which use SPF, then SPF will catch the spoofers.
-- Richard Damon