You should add an unsubcribe link to the footer of all your email surveys. If a recipient clicks this link, SightMill will mark the email address as 'unsubscribed' and will not send a survey to this address (note: this works per-Project).

If you use our 'Default' email template, the footer already includes the link

To add your own link, in the template, switch to code view by clicking the </> button and use the shortcode [unsubscribe] within an link.

For example: <a href="[unsubscribe]">Unsubscrbe me</a>

To see which contact has unsubscribed, select Settings/Email Data List and note the 'Subs' column - if it a 'Y' the contact is subscribed and will receive surveys; if it is a 'N' the contact has unsubscribed and will not receive surveys