LMi.net is now using an anti-spam technique called Greylisting on our mail servers. Greylisting has proven to be quite effective at reducing the amount of spam our servers get. It works like this: When we get an incoming email message from an email server we haven’t seen before, we temporarily reject the message, requesting that the remote server try again later. The next time the server attempts to deliver the message (usually within 1 to 30 minutes), we accept the message, and then will accept any future email from the same server on the first attempt going forward.
This technique will reduce spam because a lot of spam isn’t originating from legitimate, properly configured mail servers. It often comes from compromised computers that have been hijacked, or servers that are just designed to send out as much spam as possible. If such a server doesn’t get a response from a target mail server, then it will generally just skip it and go onto the next address in the list.
What this means for you is that there may be a delay of up to 30 minutes between the time the message is sent to when it appears in your inbox. But this would only be for the very first time.
For more information about Geylisting, see http://projects.puremagic.com/greylisting/