PLEASE NOTE : By default your cPanel account comes with Greylisting enabled. For info about how to disable Greylisting, see the steps below.
So what is this Greylisting? Greylisting is a popular and useful tool to fight spam.
How does it work? When enabled, our mail server will temporarily reject any email from a sender that your account does not recognize. If the email is legitimate, the originating server will try to send the email again after a delay. Your account will accept the email at that time and all new messages from this source will be delivered without delay.
Why does it work? Properly configured email servers will try to resend any delayed, Greylisted message and when they do, your account will accept the message. Spam servers are generally not configured properly and in most instances do not attempt to resend the message. Since the email is never resent, your account will not process or deliver the junk mail.
The cPanel interface allows you to enable or disable Greylisting for each domain on your account. To enable or disable Greylisting, follow these steps :
1. Login to your cPanel
2. Under the Email heading, click the Configure Greylisting icon
3. On the next page, you will see a list of the domain(s) associated with your account. Under Status, you will see an On or Off button. Remember, Greylisting comes enabled by default.
Click to enable or disable. That’s it!
Overall, Greylisting is an effective tool, but like with all anti spam measures, there are some drawbacks.
Initial Delays : The most obvious issue is the initial delay of mail from new senders. This delay can range from a few minutes to a few hours because the sending email server controls how quickly they attempt to resend the message. Of course, the good news is this issue is quickly mitigated once the sender is whitelisted. All future messages from this server will be received without delay.
Possible repeat delays : Sometimes detail about a valid and previous whitelisted sender changes. For example, the IP address of their sending email server might change and this will require they pass the Greylisting test once again. The process will simply need to repeat.
Possible bounces or warning messages : Unfortunately it is not just spam servers that are sometimes configured improperly. From time to time, a valid email server with older or misconfigured protocols might have issue interacting with a Greylisting server. The temporary delay initiated by our server may be seem as permanent error and the email might bounce back to the sender. Or the initial delay will trigger a warning message (not a final bounce) to be sent to the original sender. The does not mean the Greylisting will fail in this case, but it can be confusing to the sender.
If you are concerned a message from a specific sender might be delayed due to Greylisting and you wish to confirm this, you can access the mail logs for your account to take a look. Follow these steps :
1. Login to your cPanel
2. Under the Email heading, click the Track Delivery icon
3. On the next page you can see the most recent entires in your account’s mail log. You can scan these entries or use the search tool to look up logs for the RECIPIENT’S email address.
If you have any questions about what you find here, please let us know!
If you have any questions about how Greylisting works, let us know. We can help make this feature work for you.
For more complete information about how Greylisting work, see this article - https://en.wikipedia.org/wiki/Greylisting