It may happen that somewhere along the line you got yourself signed up to receive notifications from the ITS system at openldap.org. They show up quite regularly with a openldap-its@openldap.org as the From address. Then later you decided you don't want to receive them. So you send a message with unsubscribe in the body to openldap-its-request@openldap.org. Imagine your surprise when the email bounces because the to address isn't recognized.

This is because that's not the right address to use and as of the moment the mailing lists page on the web site doesn't say anything about this. What you need to do to unsubscribe is actually send an email with the word unsubscribe in the body of the message to openldap-bugs-request@openldap.org.