Yutaka-Notes about Extensible Classes In ZimbraStore
By this, you can register your custom function to be called when a messege is receive with lmtp.
Sample is here;com.zimbra.cs.mailbox.QuotaWarning
[Note]You have to register this to com.zimbra.cs.lmtpserver.ZimbraLmtpBackend
By this, you can implement to genearate custom auth token and to validate that.
Sample is here; com.zimbra.cs.service.ZimbraAuthProvider
[Note] You have to register this to com.zimbra.cs.service.AuthProvider
By this, you can add SASL mechanism for IMAP/POP. But to use the custome SASL mechanism, you also needs to customize Zimbra Proxy(Nginx/nginxlookup), which requires you to modify core code.
Sample is here; com.zimbra.cs.security.sasl.PlainAuthenticator
[Note] You have to register this to com.zimbra.cs.security.sasl.Authenticator
By this, you can implement custom function which is called right before/after a certain LDAP field is modified.
Sample is here; com.zimbra.cs.account.callback.AccountStatus
[Note] You have to register this to zimbra-attrs.xml and rebuild ZimbraServer project as far as I remember.