linkedlinked writes "I'm tired of building my sandcastles on Google's beachfront. I've moved off Docs, Plus, and Analytics, so now it's time to host my own email servers. What are the best self-host open-source email solutions available? I'm looking for 'the full stack' — including a Gmail-competitive web GUI — and don't mind getting my hands dirty to set it up. I leverage most of Gmail's features, including multi-domain support, and fetching from remote POP/IMAP servers. Bonus points: Since I'm a hobbyist, not a sysadmin, and I normally outsource my mail servers, what new security considerations do I need to make in managing these services?"