What's the best thing to do after an unsubscribe link was clicked from an email? Should I present a landing page, or just an alert box that says, "you're now unsubscribed" and redirect to the main portal?
Surely the practicalities of trying to launch an alert from an email preclude that option.
What you are trying to achieve is, initially, reassurance for the user that they have successfully unsubscribed. The most simple way to do this would be with a landing page that says something like "You have successfully unsubscribed".
However, your secondary concern is to still try to retain some sort of relationship with the user and I don't think an alert box is the way to do that - alert boxes are more associated with bad news than good news.
I would use a landing page that makes use of your site's top-level navigation (at least) and a friendly page saying how sorry you are to see them go and suggesting that maybe there's something else you can help them with before they leave. Maybe some sort of tempting offer (depending on your business model) or maybe even a quick survey to find out why they left (frequency of emails, email content, relevance...)
Maybe you avoid the unsubscribe link altogether and offer them a way to 'manage' their subscription instead - allowing them to refine the reasons/frequency you email them...
Just try to make the most out of what is potentially a bad situation.
The first thing to do is to confirm the action e.g. "You've unsuscribed"
Depending on how is designed your previous page you could:
- Provide an "Undo" action. If the unsuscribe is just a click-a-button process they user could have unintentionally click it, so giving the option to undo and suscribe again never hurts.
Ask for reasons after they reached they goal (after stating that the user is already unsuscribed and if you're not doing it in the unsuscribe page).
Instead of redirecting, let the user get the control by providing a link like "Go back to home page".