What Is Greylisting?

Greylisting is a new method of blocking significant amounts of spam based on the behavior of the sending mail server. It is used at the mail server level so it places no load on the end user's machine. Greylisting relies on the fact that most spam servers do not behave in the same way as "normal" mail servers. In testing, our Greylist has vastly reduced the amount of spam our testers received while at the same time reducing the burden on our mail servers. The only thing our testers noticed was that sometimes, with the first email someone sent them through the Greylist, receipt was delayed usually about 10 to 15 minutes, but occasionally up to an hour. After the first mail passed through the list however, receipt time was back to normal for that sender.

How Does Greylisting Work?

The Greylisting works by returning a "Temporarily Unavailable" message to the sending mail server the first (and only the first) time a message is received from a given sender. Normal mail servers, such as ours or Yahoo! or AOL, will respond to this message by attempting to resend the email. Most servers try again in 10 to 15 minutes, but some may wait up to an hour before making the next attempt. However all legitimate mail servers will retry. Because of the tremendous volume of messages spam servers are trying to send, most do not try to resend these "failed" messages; they simply give up and move on. This is how Greylisting defeats spammers.

How Do I Turn Greylisting On/Off for My Email Account?

Because Greylisting is so beneficial, we very highly recommend that everyone turn it on, or have us turn it on for you. To enable Greylisting for your account, just go to https://mailhost.idcomm.com, and log in with your full email address and password. On the following page, scroll down to Greylisting and check the box to turn it on, or uncheck it to turn it back off. Then click the Update Settings button. This will turn Greylisting on or off for your account. If you prefer, you may contact us at one of the numbers listed below, and we'll change the Greylist setting for you.