If you use GoogleAppsSync ( for Microsoft® Outlook is a plug in that allows Microsoft® Outlook to run on Google Apps rather than Microsoft® Exchange Server ) you will need to keep in mind that this tool use upload bandwidth more than pop or imap. I was set 70 google apps users and i have raised upload from 512kbit to 2mbit. I live in Croatia , country where bandwidth is very expensive, because of that i use ADSL 8mbit/512kbit and 2/2mbit leased line. All the clients use download and upload trough ADSL line, except upload for gmail going trough leased line ( add a route in smoothwall firewall ).