All current memberships of the contact will be removed and replaced by the ones given there. If you want to add or remove only specific list, please use end points /subscribe or /unsubscribe

[Optional] Require subscribers to confirm their subscription by sending a confirmation request.

Legacy Version
- message: id of the message that must be sent. This message must contain a link to $confirmUrl$
- reminder: id of the reminder message. This message must contain $confirmUrl$ as well.
- reminder_delay: if you want a reminder to be sent, specify the number of days between the first message and the reminder.
{ "message": "aw94xefgh", "reminder": "94was76ef", "reminder_delay": 34 }
Splio Edition 2025
- enabled: Enable double optin
{ "enabled": true }