Nice to see a fellow M$ admin trying to escape the dark side! <g> I hope this addresses most of your points, although not in any particular order. Forgive me, it's morning, and I'm on my first pot of coffee!
I'm currently working on a RH 8 server for work with similar problems. I'm using Postfix (www.postfix.org
), though with a single domain (gov't law firm). I like Postfix because it only has two config files, and no M4 macros to run. Right now, we're using a very basic version of qmail on one of our AS/400 servers, and it's choking it.
I've installed Squirrel mail for WWW access, and open LDAP for user authentication. There is a plugin for Outlook's C&W feature that will allow LDAP authentication, but what you're looking for is IMAP. Beware, though that users being users, some of them will *never* delete mail. With the appropriate management blessing, you may want to set a big partition for /usr, and set user quotas. In total, I've got about 225 users in five offices. I've calculated disk space for 350 users and 100 mb each, to allow for expansion.
If you're not using Outlook Express, I would suggest that for a mail client for your Windows boxen, as it has built-in LDAP and IMAP support, and is included with IE for free (just for the boss!). There will be some pain for my users in changing from O98 to OE, mostly in learning the new proggie. What fun - I get to visit all the user's workstations and set up the exchange!
10k/hour is high, but doable. Regarding failback, all that you need to do is set multiple MX records in your DNS. The primary has a value of 10, the secondary has a value of 20, the tertiary has a value of 30.
Multiple domains aren't any problem. Look up 'virtual domains', and make the appropriate entries in your DNS. I'm sure that there's some way to ghost the server, and change just the particulars you need. Personally, though I'd host them all on one machine at HQ. We've had more problems with power and UPS's failing.
Backup: This is a temporary problem for me, as a tape drive with the capacity would cost more than the rest of the machine! Right now, I'm running a cron script at 23:00, which gzips /usr, and backing up to a W98 backup "server" with a 200 gb IDE drive and an IDE tape drive.
Replication. Did you look into mirroring software?
Group calendar. That's a problem I haven't solved either. For me, there are a couple of requirements: 1.) Multiple accesses to a person's calendar, so a secretary can add appointments to an attorney's calendar. 2.) The ability to sync with Palm. 3.) The BIG BOSS wants to be able to read anyone's calendar. Ideally, it would tie into the person's web/IMAP mail calendar.
User authentication: With Samba, they use the same NT domain logins and passwords that they use at work. I'm trying to convince the PTB to authorize individual passwords and password rotation, instead of a common password that everyone uses. (I know it's bad security. I inherited it, and it's something I'm fighting.) With the advantage of webmail, I think I can sell it from the liability standpoint of a cracker or spammer hacking someone's account. Any suggestions in that regard?
Anyway, I hope this helps!
karanne AT mindspring DOT com