Greylisting FAQ
What is Greylisting?
Greylisting is a simple method of defending electronic mail users against email spam.
Will this slow down my mail?
Greylisting will not cause email sent from Cal Poly severs to be delayed. However, while the database of acceptable addresses is built up, there will be an initial delay for email coming from the Internet. This delay depends upon the sending email server's configuration. The initial wait will be at least 5 minutes, but may be longer. We are setting user expectations for anywhere between 30 minutes and 24 hours. If a sending email server does not retry sending an email, the message will eventually be bounced to the sender as undeliverable. Once the triplet is in the database there is no delay caused by greylisting.
What email does Greylisting affect?
Greylisting is a technology installed on the campus email gateways. Email addressed to user@calpoly.edu is processed by these gateways. Some other campus email servers have already configured their servers email to route through the gateways as well. If you are unsure please call the Service Desk or ask your email administrator.
Is there another way of validating the Internet email servers without this potential delay?
Yes, there are a number of projects being worked on by different companies and groups across the world. No single technology has become the standard. We are constantly evaluating different technologies to reduce unwanted email without losing valid email.
What will the person sending the message see if Greylisting delays their email?
In most cases the email sender will see nothing. A normal part of email is the potential for a delay if a server is unavailable. The Internet standard for email servers supports retrying a message numerous times for at least 24 hours. Some email servers not following the Internet may be configured to only try once, and if the email server is unavailable to return the message to the sender. If this happens please create a Remedy ticket requesting a whitelisting for that server and we will allow that email server to send messages without delay.
Is it possible for legitimate emails to get lost?
No. The email will either be delivered to it's final destination, or will be bounced back to the person who sent it originally. If the email gets returned to the sender. They may resend it manually. This will also complete the triplet and allow future emails to be successful. If an email that was supposed to go to you is bounced back to the sender, please create a Remedy ticket requesting a whitelisting for that server and we will allow that email server to send messages without delay.
Why don't the people sending SPAM just send their email twice? That would get it passed the greylisting.
Yes, but it would also reduce the number of people that a Spammer could send to by 50%. The goal in anti-spam techniques is to increase the cost of sending their email so that it is no longer a cost effective method. At this time very few sites use Greylisting, so it would not be worthwhile for people sending SPAM to send all their mail two times.
Will this fix the SPAM problem?
No. SPAM is a problem that will be around for some time. Hopefully, technology and legislation will eventually lessen the problem. At this time it is an arms race betweeen the people sending SPAM and the people trying to lessen its affects. The only way we will ever stop getting SPAM is when people quit buying things sent to them in SPAM.
