Your login for our support center is different than your Control Panel login.

Click here to create a login for the support center

FAQ - Suppression List

We often hear our customers ask "What is the Suppression List?" after finding out a message was not delivered due to suppression.  The suppression list is a tool for reputation management.

Many major mailbox providers (Gmail, Hotmail, AOL, etc) calculate and maintain reputations for IP addresses and domains.  Some of the factors that go into this reputation are invalid address delivery attempts and complaints from end-recipients.  To protect your account from attempting delivery to bad addresses or any users that have previously complained we maintain a Suppression List for your account.  This will prevent delivery attempts to any address on this list. It will help ensure you maintain a quality reputation and help increase inbox delivery rates.  Here are some of the most frequently asked questions about this feature:

Q: What makes an address appear on the Suppression List?

A: There are two ways any given address will end up on your Suppression List:

  1. The person receiving the message hits the SPAM button in a browser/client that supports Feedback Loops.  These will appear in your list as "Complaint" and will also show in your complaints report, if it occurred in the last 90 days.
  2. The receiving mail server responded with a "5xx" level permanent error response, such as: "550 5.1.1 User unknown In response to the RCPT TO command."  This is most commonly encountered when attempting to deliver to an address that does not exist.  The specific date and reason will always be listed with the address in your Suppression List page.

Q: How do I get a user off my Suppression List?

A: If a user is on your suppression list due to hard failure/permanent error such as "550 5.1.1 User unknown In response to the RCPT TO command", the user can easily be removed by accessing your suppression list in the Control Panel and clicking the "Remove" button next to the address in the list.  To get to the Suppression List page, log into the Control Panel and select the server you would like to manage.  Once you have selected a server, along top menu bar click Configuration and then select "Suppression List".

If the user is on your suppression list because of a feedback loop or complaint you cannot remove the address without their confirmation.  Clicking the "Remove" button next to a complaint address will bring up a form to fill out which generates a message to the address. This message includes a link they can click to opt back in to receiving messages.  This form is designed to be used when a user directly requests to receive messages again.  The form is not intended for sending unsolicted opt-in requests.  Abuse of this process can result in account suspension or cancellation.  Below is a sample message that is sent to the user:  

*** SAMPLE ***

We recently received a request that you would like to receive e-mail messages from us again.

Your email address was put on our do-not-email list because we had received a report that a message from us to your address was marked as SPAM. This can happen if you accidentally clicked the spam button on one of our messages. Follow the instructions below to remove your address from this list. Also keep in mind that marking items as SPAM once more will cause your email address to be placed back on the do-not-email list.

For security purposes you need to confirm your desire to receive these messages by visiting the following URL:

Thank you,


This service is provided by SocketLabs On-Demand. To report abuse of this service, please send an email to


Q: Can SocketLabs turn off the Suppression List feature for my account?

A: Under certain circumstances we can turn this off for accounts in good standing.  Contact for more information. 


Q: Why did this user end up on my Suppression List for what should be a temporary failure?

A: Not all mail servers respond with the same error code, and some may indicate a temporary error such as "Mailbox Full" with a 5xx level response.  If this occurs and the user is on a suppression list incorrectly, please alert about the issue and we will create a custom rule to handle that exact response to prevent the issue in the future.

Help Desk Software by Kayako  Copyright © 2019 SocketLabs, Inc.  Terms of Service | Privacy Policy | Acceptable Use Policy