Overview
Transactional Email offers sending emails via IP registered to the Certified Sender Alliance. By doing, so, the inbox placement is improved when delivering emails to Internet Service Providers and Mailbox Providers part of the CSA Partnership (official Participants list).
The CSA feature has been meant as a control setting to make sure emails sent via CSA-certified IPs comply with Certified Sender Alliance criteria. Among other technical requirements that Retarus handles during Onboarding phase, the CSA feature enforce the following conditions:
-
List-Help header when sending non-list-based, transactional emails;
-
or List-Unsubscribe header when sending list-based, promotional emails.
The subsequent selection of the appropriate header depends on the content of the email to be sent and is the responsibility of the Transactional Email end-customers.
Feature activation
By default, the CSA feature is not available upon Technical Account creation. Only a Retarus Admin, via a Support Request, can enable and configure it in case CSA-certified outgoing IPs have been booked. Depending on the mailflow typology to be processed through the Technical Account and assigned Sender Domain(s), the CSA feature will be configured accordingly.
How to use the feature
During Processing, the CSA feature configuration will be tested against the incoming message. If the JobRequest fails the validation of the configuration, the request is synchronously rejected. Every email sent must contain either a "List-Unsubscribe" header or a "List-Help".
List-Unsubscribe
The "List-Unsubscribe" header is required for promotional/list-based mailing and must be inserted with a "POST HTTPS" link including "One-Click-Unsubscribe". The specified link must enable direct one-click unsubscription at least at list level.
Example of valid inserted headers:
List-Unsubscribe: <https://example.com/unsubscribe/abc123>
List-Unsubscribe-Post: List-Unsubscribe=One-Click
Special: to fulfill with Bulk Sender best practices as well, when a List-Unsubscribe URL is detected for a REST JobRequest, a “List-Unsubscribe=One-Click” value for the List-Unsubscribe-Post header is automatically added before sending.
List-Help
For transactional/non-list-based mailings, the "List-Help" header must be set as an alternative to the "List-Unsubscribe" header. The "List-Help" header must contain at least a "mailto:" address or an HTTPS link. HTTP links are not permitted. Both the use of the "mailto:" address and the HTTPS link must give the recipient the opportunity to receive information about the reason why the email was sent to them and why it is not possible to unsubscribe at list level.
Example:
with an email address:
List-Help: <mailto:help@example.com?subject=help>
with a HTTPS link:
List-Help: <https://example.com/help/newsletter>
with both:
List-Help: <https://example.com/help/newsletter>, <mailto:help@example.com?subject=help>