We ran our own mail server for years using linux and a spam filtering software I can't remember. While I would prefer to have my email on my own box the abilities of Gmail are pretty amazing. I see far less spam than before what I do see is a bunch of people that don't know their own email address giving my email to their friends, school, kids school, car dealership, accountant (yes got someones tax return), pharmacy notifications. My biggest gripe is the number of companies that don't conduct email verification before signing someone up for something.
Of course if I would just pay for the services to host my domains email addresses then I would not have to deal with this instead of spoofing the outbound address.
BTW a company that I conduct contract work for uses Gmail and it works great as well, but has many of the features to administer users content such as the required signature, logo, required photo ect. But all of this is quite off topic for the list as it seems to work for gmail, yahoo ect. Lin N4YCI