[Enhancement: Jetpack Newsletter] Notify users when adding duplicate subscribers

[alinclamba]

Impacted plugin

Jetpack

What

Enhance the subscriber import process by notifying users about duplicate entries upfront, reducing confusion and streamlining the experience

How

When trying to add a new subscriber who is already subscribed, the process currently fails silently, and the user receives an automated email stating there was a problem, asking them to contact support. This creates unnecessary confusion and adds friction for both users and support teams. Here's what the email looks like:

What if we improve this, and here are two suggestions.

1. If possible, display a clear message in the subscriber form when a duplicate email is entered (e.g., "This email is already subscribed"). The import form could look like this:

2. If real-time validation in the form is not feasible, can we update the automated email to include the reason for the failure (e.g., "The email you tried to add is already subscribed."). We already have that info in our logs, showing why the import failed. Since we have this info in our logs, it would be helpful to share that info with the user quicker, in the automated.

Notified internally: p1734944097876859-slack-C083ZPVVDTK

[github-actions]

OpenAI suggested the following labels for this issue:

• [Feature Group] User Interaction & Engagement: The issue focuses on enhancing user experience by providing timely notifications about duplicate subscribers.
• [Feature] Subscriptions: This issue relates directly to the subscriber management process in Jetpack.
• [Feature] Notifications: The enhancement involves notifying users when they try to add a duplicate subscriber, which falls under notifications functionality.