32GB of storage satisfies 18 users? That surprises me. I have 5GB in one mailbox and I'm not much of an e-mail hoarder. Also, what do you do for backups? Do you have offsite backups? How do you search your email? How do you filter spam? What about calendars, shared contacts, and internal document storage? Do you have multi-factor auth and application-specific passwords? Google Apps has a ton of features and it's reliable. Not to mention, it's cheap. Unless your time is worth very little, setting-up and maintaining your own mail server is going to cost a lot more.
People use e-mail constantly. It's important. $50 per person per year isn't a blip on the radar. Do you know how much money you'll lose if your 18 users can't access their mail for an hour? Now consider how much time they'll spend setting up their own mail clients instead of using Gmail. Think of the increased time and frustration waiting for searches to finish. Think of the extra time they'll spend deleting spam. You're paying a lot more than $40-50 for that mail server, but the real cost is obscured from you.
It's a no-brainer: skimping on email hosting is simply not worthwhile.
Our biggest mailbox is 200mb. Pretty much everything gets deleted or moved out of the mail system. It's not a file system. If you think it is, you're doing it wrong.
Backups: tar and gzip daily, then scp to a friend's server in another country. Also take manual backups to encrypted USB stick weekly which I carry around on me at all times.
Searching: you only have to search it if you have lots of it. I have 9 messages in my maildir. I receive perhaps 20-30 messages a day. No problems - they all fit on the screen. If it's worth keeping, it goes as a ticket/wiki entry or in the hg repo as a document.
Spam: get one or two a week per user. Just delete by hand at the moment. People who use imap use their mail client's spam filtering stuff. If it gets problematic I'll probably install a filter.
Calendars/contacts: both in mercurial in agenda format (plain text, one line per event or contact). Very easy to manage and share. Have you tried keeping a central address book/calendar accurate using any other method?
I know how much we'll lose without email which is why it is where it is :) About 2m from me most of the time.
Cost? I've spent 20 minutes on admin this year. Everything is automated..
I'm not skimping, I'm making sure we do it right so we don't need all the tooling and features. To be honest, google is too cheap to be good if you ask me and their reputation shows regulalrly with outages and problems.
I can appreciate that for most people this is not a decision. But for technically inclined people who want to learn this stuff, there's no reason to talk them out of it. Is it substantial work? Yeah, but so is running a web server or a database and those are also critical IT components that have a lot of niggling details.
There are lots of reasons to not use Gmail. Maybe $50/year is a lot for you. Maybe your needs are modest. Maybe you want the knowledge and experience of running mail. Maybe you want or need to interface your other components with mail. Maybe you don't like the rest of Google Apps. Maybe you hate the Gmail interface. Ultimately, most people will choose Gmail despite whichever of those reasons might apply. There's no need to turn a technical decision into a dogmatic one.
People use e-mail constantly. It's important. $50 per person per year isn't a blip on the radar. Do you know how much money you'll lose if your 18 users can't access their mail for an hour? Now consider how much time they'll spend setting up their own mail clients instead of using Gmail. Think of the increased time and frustration waiting for searches to finish. Think of the extra time they'll spend deleting spam. You're paying a lot more than $40-50 for that mail server, but the real cost is obscured from you.
It's a no-brainer: skimping on email hosting is simply not worthwhile.