EXM: Adding "List-Unsubscribe" header to emails

Question

We are currently trying to improve spam-scores for our customers' email campaigns and have used the tool https://www.mail-tester.com/ which states that we are being penalized by not including a List-Unsubscribe header/functionality.

Does anyone know (or have implemented) functionality to the EXM pipeline that adds the List-Unsubscribe header to emails? Googling and the Sitecore knowledge base has failed me so far.

Answer 1

Assuming you're using EXM 3.3 (or later) this can be done by overriding the dispatchprovider. You'll find this element under /sitecore/exm/eds/dispatchManager in the configuration (Sitecore.EDS.Providers.CustomSMTP.config or Sitecore.EDS.Providers.Dyn.config) e.g.

<dispatchManager defaultProvider="default">
    <providers>
        <clear />
        <add name="default" type="Sitecore.EDS.Providers.CustomSmtp.DispatchProvider, Sitecore.EDS.Providers.CustomSmtp">
            <param ref="exm/eds/connectionPool" />
            <param ref="exm/eds/environmentIdentifier" />
        </add>
    </providers>
</dispatchManager>

You'll need to override the SetMessageHeaders method e.g.

protected override void SetMessageHeaders(EmailMessage message)
{
    base.SetMessageHeaders(message);
    message.Headers.Set("Your-Header-Name", "Your-Value");
}

In EXM 3.4 and later, this configuration element has changed and is now called

<dispatchProvider defaultProvider="default">
  <providers>
        <clear />
            <add name="default" type="Sitecore.EDS.Providers.CustomSmtp.DispatchProvider, Sitecore.EDS.Providers.CustomSmtp">
                <param ref="exm/eds/connectionPool" />
                <param ref="exm/eds/environmentIdentifier" />
            </add>
    </providers>
</dispatchProvider>