Unsubscribe mechanism

CodeTwo Exchange Rules Pro comes with a built-in unsubscribe mechanism that allows you to stay compliant with the latest regulations concerning email disclaimers and user privacy. When this unsubscribe mechanism is configured and enabled, the program inserts the {unsubscribe link} placeholder to all emails sent externally. Once the recipient clicks the unsubscribe link, their email address is added to a blacklist, which prevents them from receiving any further emails from your organization.


By default, the predefined unsubscribe mechanism applies to all users in your company. However, you can narrow it down to selected users, groups, and make other changes to it. Learn more

This article contains the following sections:

The flow of operations in the unsubscribe mechanism

The flow chart below (Fig. 1.) illustrates how the unsubscribe mechanism works:

  1. The Unsubscribe mechanism is configured and enabled in the Administration Panel.
  2. One of the users in your organization sends an external email.
  3. CodeTwo Exchange Rules Pro processes this email and inserts the unsubscribe link.
  4. The recipient receives the email with the unsubscribe link. If this recipient decides to unsubscribe from your company's mailing list, they click this link.
  5. The information about unsubscribing from the mailing list is sent to the Unsubscribe Service, which processes this information and adds the recipient's email address to a blacklist.
  6. The Exchange Rules Pro Service synchronizes the recent changes in the blacklist data from the Unsubscribe Service.
  7. One of the users in your organization sends another email to the recipient whose email address has been added to the blacklist.
  8. The program blocks this message, and the message does not reach the recipient's inbox.
ER Pro 2.x - Unsubscribe mechanism scheme big.
Fig. 1. The flow chart of the unsubscribe mechanism.

Rules and services involved in the unsubscribe mechanism

The unsubscribe mechanism uses the following rules and services to unsubscribe recipients from mailing lists:

The unsubscribe mechanism rules

The unsubscribe mechanism can be quickly added from the Administration Panel. The mechanism is based on a combination of two rules:

Unsubscribe mechanism - Unsubscribe link

This rule inserts the {unsubscribe link} placeholder into disclaimers, and is applied to all emails sent externally. By default, this rule includes one condition Recipient is external (Fig. 3.).

Fig. 3. The default conditions of the Unsubscribe mechanism - Unsubscribe link rule.

Recipients who have already been included in the blacklist, either by clicking the unsubscribe link in the past or because they have been added to the blacklist manually, are already excluded from receiving the email with the unsubscribe link (Fig. 4.).

Fig. 4. The exception that prevents sending emails to users who are already on the blacklist.

On the Actions tab, the rule contains the Insert disclaimer action with the {unsubscribe link} placeholder (Fig. 5.).

Fig. 5. The Insert disclaimer action with the {unsubscribe link} placeholder included.

Unsubscribe mechanism – Block message

This rule prevents sending emails to a recipient who unsubscribed from your mailing list. This rule includes two Recipient conditions (Fig. 6.) configured in the following way: Recipient is external and Recipient belongs to blacklist [name of the blacklist]. These conditions are bound with the default And operator, so that they both have to be met for the rule to apply.

Fig. 6. Two recipient conditions that are bound with the And operator.

The rule also contains the Block message action (Fig. 7.). It blocks emails according to the conditions specified earlier.

Fig. 7. Blocking the recipient from receiving further emails from your organization.

The Unsubscribe Service

The Unsubscribe Service (unsubscribe.codetwo.com) is hosted on Microsoft Azure and performs the unsubscribing action:

  • removes the recipient from a mailing list,
  • adds the recipient's email address to a blacklist, and
  • makes sure that the recipient does not receive unwanted emails.

The unsubscribe mechanism creates separate blacklists for each organization that uses the Service. To ensure that the Service is GDPR compliant, all the data kept by it is anonymized and encrypted. The encryption key is based on a unique value from organization’s AD. No one apart from you can decrypt and read information stored in the Unsubscribe Service.

The Unsubscribe Service comes with the program, so you do not need to implement any other services on your end to use the unsubscribe mechanism. Using CodeTwo Unsubscribe Service is safe because the communication between this service, the Exchange Rules Pro Service and your private data is protected via three independent technologies: AES encryption, SHA-1 cryptographic hash function and RSA key transport algorithm.

The Exchange Rules Pro Service

The Exchange Rules Pro Service synchronizes the recent changes in the blacklist from the Unsubscribe Service with your instance of the program and triggers the Block message action.


The communication and synchronization of data between the Unsubscribe Service provided by CodeTwo (unsubscribe.codetwo.com) and the Exchange Rules Pro Service is executed via port 8080. Make sure that this port is open for outbound traffic. If the port is not open, you might receive the following error message (Fig. 8.).

Fig. 8. This error is displayed when port 8080 is blocked.

Management of blacklists

You can manage the blacklists (and the recipients included in these lists) in the Administration Panel. Making changes to your blacklist can be required in two basic scenarios:

  1. You already know that there are clients who no longer want to receive emails from your company. In such a case, you can create a blacklist and add those clients' email addresses to this blacklist, so they don’t need to unsubscribe from your list again.
  2. Some of your clients, who already unsubscribed from your mailing list, change their minds and want to resume receiving emails from your company. In such a case, you can remove their email addresses from the blacklist.

To manage the recipient blacklists, go to the Administration Panel, click the Settings button on the toolbar and navigate to the Recipients blacklists tab (Fig. 9.).

Fig. 9. The recipients blacklists tab in program's settings.

The tab is divided into three sections:

  • Recipients blacklists - here you can manage (Add or Remove) your blacklists. Each blacklist includes a list of email addresses of recipients who unsubscribed from your mailing lists.
  • Email addresses in this blacklist - this section lets you manage (Add/Remove/Edit) the individual email addresses (in the SMTP format) included in the blacklists. Note that email addresses are automatically added to this field once a recipient of your email clicks the unsubscribe link in the message. If you want to add more email addresses to a chosen blacklist, you can provide them here. In addition, you can either type full SMTP email addresses or use wildcards. When using wildcards, you can include the asterisk (*) in front of, after, or inside an email address, e.g.: *@company.com, newsletter@*, newsletter@*.com.
  • Import / Export buttons - these two options let you import or export the existing blacklists and the included recipients to any other instance of the program (e.g., operating on a separate tenant within your organization).

See next

How to configure the program to enable unsubscribing recipients from mailing lists

Was this information useful?