What is greylisting?
When an email server attempts to
send email to your account we send back a specific error code,
indicating that we are temporarily unable to accept the mail. This
doesn't mean your email is lost though.
Normal email servers know to retry again, almost
immediately. On the second mailing attempt our system knows that this
is probably genuine and accepts the email. We also record the IP
address of the email server and 'whitelist' it. This means we then
accept all future email with no further checks.
Most spam is sent through compromised PCs or
mailing systems setup to send as much spam as possible, so they will
not correctly handle the temporary error code. The server is simply
trying to send as much spam out as possible and as a result doesn't try
to resend the spam email to you after receiving the temporary error
code.
A slight delay is introduced with this system, but
not much! When we reject the initial email connection it is then down
to the sending mail server to retry sending the email. The actual
period of delay between the first and second attempt is down to the
sending server. As an example 34SP.com servers retry after 20 minutes.
Other email servers may be faster or slower than this, but all genuine
mail servers will retry.
This delay only happens once for each of your
regular contacts. If the same email server sends mail to you again they
will not be challenged. All successful mail server connections are
logged (with the IP address of the mail server stored) and held for a
36 day period. This is a rolling 36 day period from the time of the
last mailing, so if you have someone that regularly mails you it is
unlikely that their email server will be challenged more than once.
For greater peace of mind our system is also
capable of running whitelists on an IP address. If someone mailing you
is having difficulties, we can easily whitelist their IP address. Their
email will then no longer be challenged and will be automatically
accepted.
It should be stressed that all genuine email comes
from servers that are correctly configured and can handle this system.
The full details regarding the greylisting method can be found in the
whitepaper by Evan Harris.
How to enable greylisting
1) First login to our site
2) Once logged in select "products" from the right hand menu
3) Next select "Hosting"
4) Select the "Upgrade" option opposite the account to enable
4) From the dropdown select "Greylist management"
5) Finally change the select to "Yes"
The upgrade is free and will be enabled within 60 minutes of your activation on our site.
Article ID: 61, Created On: 8/14/2008, Modified: 12/15/2009