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Email - Greylisting FAQ

This article answers some frequently asked questions about Greylisting, a spam filtering technique.

What is greylisting?

Do you mean I'm going to get two copies of everything?

Won't the spammers just send the message twice?

Will the person sending the email need to do anything?

Will this solve my junk mail problem?

Will this delay my email?

Does this affect email sent from another University of Chicago email accounts?

Will greylisting block valid email messages?

Does greylisting replace the Junkmail service?

Will greylisted messages show up in my quarantine?

Can I turn off greylisting?


What is greylisting?

Greylisting can significantly reduce junk mail by requiring unfamiliar email servers to re-send a message before accepting it for delivery. Most automated spam servers will not re-send on request, thus eliminating many unwanted messages. However, servers that comply with email standards will re-send their messages, allowing them to pass through the barrier and arrive in your email box.

Do you mean I'm going to get two copies of everything?

You will only get one copy of a message, which you'll receive after the email service re-sends the message.

Won't the spammers just send the message twice?

Eventually, spammers will come up with a way around greylisting--and yes, sending everything twice is one such way (though it's a bit more complicated than that at the technical level). At present time, however, most spammers do not adhere to Internet standards when sending their email and greylisting will work as long as that is the case.

Will the person sending the email need to do anything?

No. Email servers that comply with email standards will re-send their messages without the sender having to do anything.

Will this solve my junk mail problem?

It depends on the type of junk mail that you receive. It will eliminate spam from email servers that do not conform to Internet standards.

Will this delay my email?

The first time a given remote email server tries to send an email message to an @uchicago address, email will be delayed until the remote server re-sends that message. (Typically, this will be 5-20 minutes, but it depends on the configuration of the remote server.) Once the remote server re-sends the message and is added to the approved list, email from that server will flow normally again.

Does this affect email sent from another University of Chicago email accounts?

No. This only affects email sent from email servers outside the University with which we have not had previous contact.

Will greylisting block valid email messages?

Greylisting blocks all messages that do not comply with email standards. If someone sends you a "valid" email message from an email server that does not comply with email standards, greylisting will block it.

Does greylisting replace the Junkmail service?

No. Greylisting works in conjunction with the Junkmail service. Greylisting is just an additional way we are blocking spam from University email accounts.

Will greylisted messages show up in my quarantine?

No. Messages that are not re-sent don't come in contact with our servers, and therefore are not added to your quarantine.

Can I turn off greylisting?

No. Greylisting is set up for the entire central email system.




Keywords:spam filter junkmail email messages junk mail greylisting quarantine problem block   Doc ID:16173
Owner:Lane W.Group:University of Chicago
Created:2010-12-07 18:00 CSTUpdated:2016-10-13 12:47 CST
Sites:University of Chicago, University of Chicago - Sandbox
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