Easy, anonymous unsubscribe
One way to handle this is to provide an easy and anonymous unsubscribe link in your outgoing email. Assign each user an id number that differs from his or her email address, and keep some sort of database (even if it's just a spreadsheet) of these userids. Then create a link in your mailings that automatically unsubscribes people based on ID, like this:
Now, users just have to click once on the link, and they are unsubscribed without having to reveal their email addresses.
This technique is also very handy when you are faced with a spam report.
Every spam report includes a copy of the spam, so you can just click the
link, and know that the person has been unsubscribed without having to grep through logs files.
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