What is Zimbra pre-authentication and how does it work?

Zimbra pre-authentication allows you to log into a user's mailbox using a pre-shared key (PreAuthKey) instead of a password. It works by computing an HMAC-SHA1 hash from the username, timestamp, and an expiration value, then passing this token in the URL or SOAP request. For a detailed walkthrough, see the [Zimbra SOAP API Development Guide 6 - Pre-authentication](/news/zimbra-soap-api-development-guide-6-pre-authentication1).