Use a Pi2
I've been running email servers at home ever since I got ADSL. I now use an rPi2 with an external disk. I use postfix with dovecot with an auth'd submit port and IMAP over SSL with external inbound access. My rpi2 is a hidden gateway so and have two externally facing SMTP MTAs running on cheap VPSes (£3 pm also used for web servers, dns, etc). On those servers I only run postfix with DNS blacklists (zen.spamhaus.org and bl.spamcop.net), OpenDKIM to get more mail through to some servers (some will greylist you unless you have a valid DKIM sig) and postfix anvil (to prevent those annoying dict'-based email attacks). I don't use any AV - I get hardly any SPAM ever. Works a treat. The servers hardly break a sweat ever. I have a long queuing time on the externally facing servers so my rPi2 can be down for up to a month before a mail is bounced - good when away on long hols if my adsl fails. You really have to make sure you choose your VPSe/VMs well; Need to make sure your IP or AS isn't blacklisted and must have reverse DNS setup. On top of this I use a different email address for every company or org I deal with. Just cut them off if they don't honour the unsubscribe etc.