As standard, we include the List-unsubscribe tag in the technical header of all marketing emails sent from the platform; you don't need to add it.
Here's an example of what it looks like in iOS.
What are the benefits of List-Unsubscribe?
It's good for two reasons:
It makes it easier for recipients to leave your mailing list if they wish to, as the unsubscribe option is more prominent in the header as opposed to being buried away in the body of the email
It encourages recipients to unsubscribe from the content they don’t want to receive, rather than mark the email as spam/junk. Spam reports can severely damage your and our sender reputations, or, worse still, lead to block listing.
Aren't recipients more likely to unsubscribe with the option placed at the very top?
It depends. The aim of the button is to stop complaints, and if you’re getting complaints then you need to ask yourself why that might be. Is your content poor and irrelevant? Are your sends badly timed? Are you sending to bad data (such as purchased contacts or very old subscribers)?
If your answer is yes to any of those questions then you're probably at risk of losing people, but that’s not necessarily a bad thing. Understanding why they’re complaining (or unsubscribing) is much more important, and this information can be gleaned through the unsubscribe process. It's better to lose the people who risk ruining your reputation and focus on those who want to hear from you.
If you're collecting and using good data (which you should be doing), and your email content is timely and relevant, then having an unsubscribe option at the top won't affect anything.
Can I edit what the List-Unsubscribe message says, or make it link to my preference centre?
No, it can't be customised in any way or redirected to your preference centre.
Email clients detect the List-Unsubscribe header in the email and then display it their own way.
I've sent a test to myself but I can't see the option to unsubscribe in the header. Why is that?
This could be for one of two reasons:
Support of List-Unsubscribe varies across email clients, so it may be the case that the email client you've tested with doesn't support List-Unsubscribe at all.
Email clients may only display List-Unsubscribe for senders that are considered to have a good sending reputation, otherwise, it won't be shown.