Currently it's a pain in the rear to manage users and mail accounts on my network. Poor planning on my part, but really it has more to do with being unfamiliar with eGroupware when I implemented it. I actually had to write myself a set of instructions to follow each time I add a user to the network, which is quite embarassing actually.
I have a Windows 2003 server that authenticates Windows clients through Active Directory.
The majority of our file shares occur between a Windows PC and a Linux server, so I've implemented NFS and installed the NFS tools for Windows on each of the Windows clients.My Linux clients have been authenticating over NIS. eGroupWare pulls authentication for users from NIS as well, but it doesn't have the ability to add new accounts or change passwords. I'm using Cyrus for mail, so that requires another step where the user mailbox has to be created.
So, I got a wild hair today, since I had all these virtual machines lying around, and created a virtual LDAP server for testing. I was able to migrate my network user and group lists into it very easily, but I haven't found a way for it to import all the password information from my NIS server's shadow file.