Gmail is working fine. I retrieve from Gmail into each workstation and I really like the ability to be able to look at e-mail in the gmail format away from the office. The search is great and I have different coloured labels set up for things like different listservs so they jump out. I also like the idea of having an offsite store of all my messages. I have had some duplicate situations of double e-mails when I send e-mail directly from gmail but I do this infrequently. I sync my TM to Outlook and sync Outlook to the Google calendar and this seems to work pretty well. I do n ot particularly like the google calendar though.
I guess there is some question about Gmail security but I have questions about e-mail security in general so I am not worried. One drawback is that I have the auto check of e-mail set up for every couple of minutes and gmail can be a little slow sometimes so I have frequent messages popping up about being unable to connect to the email server.
We used exchange for several years then I completely got away from it and just used TM connected to POP and lately I have been experimenting. I went with a hosted exchange that I liked but it was expensive. I did like Sharepoint and the outlook integration. I intend to do this internally when my new server with SBS premium arrives next week and I will probably go with cemaphore. I like the Outlook mail reader and the Outlook calendar and I like the gemail search ability and offline access. I don't have fixed IP so I Can't get to my server easily outside the office. I would prefer to use an outside server if possible anyway so as to avoid having all my eggs in one basket.
As to intranet I've used Sharepoint, Google and Joomla - I like Joomla - see
www.Brookelaw.com but internally I think Sharepoint is the best solution especially with outlook. I don't have Joomla on my local server but it seems slow and not as well suited for an intranet as Sharepoint but it is great for external use.