Greylisting

What is Greylisting?
Greylisting is a spam fighting tool that makes sure that an email sent to the server is legitimate.
It does this by temporarily rejecting any email from a sender it does not recognize. If the email is from a legitimate sender, the sending mail server will retry to send the email.
Many mass email tools used by spammers do not queue and reattempt mail delivery like normal email servers would.

How does Greylisting working?
Greylisting identifies incoming email by "triplets".
A triplet is a collection of three pieces of data: the IP address, the sender's address, and the recipient's address.
By deferring unknown triplets, Greylisting filters spam and allows legitimate email a second chance to pass through.

What email is delayed?
Any new email received by an unrecognized source is delayed.
However, emails from a host with a valid SPF record are delivered automatically and not deferred.

How long are emails delayed?
Email from unrecognized sources without a valid SPF record are delayed 10 minutes.
As long as the sending mail server retries to send the email after 10 minutes, the email is delivered.

Greylisting is turned ON by default for all new domains added after October 4, 2018.
Domains added before October 4, 2018 will have Greylisting turned off.

How can I turn on Greylisting to help reduce Spam?
1. Log into your cPanel.
2. Under Email, click on "Configure Greylisting".
3. Next to the domain that you want to turn on Greylisting for, click "On".

How can I turn off Greylisting if I do not want to reduce Spam?
If you do not want to have Greylisting on and reduce unwanted spam, you can turn Greylisting off in your cPanel.
To turn off Greylisting:
1. Log into your cPanel.
2. Under Email, click on "Configure Greylisting".
3. Next to the domain that you want to turn off Greylisting for, click "Off".