How to disable and manage greylisting spam protection in Plesk

This guide discusses how a mail greylist protects you from spam and describes how to troubleshooting issues with Plesk’s greylisting, and how to disable the greylist functionality for your domain, should it be interfering with receiving emails.

Greylisting protects your domain from spam by declining the first connection attempt from the sending server, and then accepting a later connection. This works to protect against spam because most spammers only attempt sending once.

There are three potential downsides to greylisting:

1. Delayed Emails: it can cause delays in receiving emails. Most mail servers default to a 5 minute retry period, so the delay is typically 5 minutes or less. However some mail servers may use non-standard retry times, making the delay longer.
2. Round Robin Issues: Some senders use multiple servers for sending email and retry sending using different servers. This can cause messages to not be received because the greylisting system counts the number of delivery attempts based on the sending server address; different servers would result in different addresses and therefore separate counts.
3. Single Attempt Issues: Some senders defy the email protocol and only attempt sending once. When sending servers are configured against protocol like this, the message being sent can’t be received because greylisting relies on standard mail retry principles.

We will often recommend disabling greylisting as a test. If it solves your problem with delayed or missing messages and the sender is a mass-mailing service or larger company, please send us the necessary diagnostic data to have us whitelist their mail servers, using the steps at the bottom of this article. Once we have whitelisted the sender, you can re-enable greylisting to continue taking advantage of its spam protection capabilities.

You must be the administrator of your web hosting account to follow these steps. If you are not, you will need to ask your domain administrator to complete them for you. Mail account owners cannot disable greylisting themselves because it is a domain-wide change.

Please complete the following steps to disable greylisting in Plesk:

1. Log in to Plesk
2. Choose the “Mail Settings” button under the domain you wish to adjust
3. Uncheck the box beside “Switch on greylisting spam protection for all mail accounts under this domain” and click OK

Greylisting will now be disabled for the domain.

If interested, you can read more about how greylisting works on Wikipedia.

How do I send diagnostic data for whitelisting?

Please log into your Websavers account, open a ticket, and include the following necessary information. Without all of this information we will be unable to whitelist the sender.

1. The anticipated email address or domain of the sender.
2. The email address of the recipient (your email address)
3. The date and time you either did receive the message or expected to receive the message. Preferably to within a 30 minute window.

We’ll then assess the sending address with the ultimate goal being to add it to our public whitelist expansion on GitHub, then apply it to necessary servers.