Interspire Email Marketer includes the ability to generate a "modify details" form link for each newsletter, so your contacts can simply click this and then change their name, email and also choose which lists (single or multiple) they would like to unsubscribe from.
In order to protect contacts from unsubscribing accidentally, Interspire Email Marketer v5.6 (and above) includes an unsubscribe placeholder at the bottom of your email. When a contact clicks the unsubscribe link, in the placeholder, they will be presented with a list of mailing lists from which to unsubscribe, simply by ticking the checkbox next to each list and clicking the "Save" button.
