Before going in-house, the first thing to consider is if you have the tolerance to build the thing. In most cases, it is pretty easy to get the software up and running. It could take weeks or months, but it probably won't take years to get some storage, some servers and a new archiving application up and running. Similarly, it's not going to take all that long to pick one.
There are a lot of choices and a lot of them are pretty good, so it's just a matter of going out there and picking one. The real problem lies in what you are going to do with this and how you are going to make it work for you. Unless you're just doing it for IT storage-reduction purposes, in which case you can pretty much implement an out-of-the box solution.
If there is any business or legal requirements for archiving, you're suddenly going to have to start thinking about what IT needs in terms of legal holds, what is the policy for records retention and how do I apply that with this particular archiving solution that I have? That can be real hard to match up. It can be very difficult to match up the expectations of legalities with the reality of the software. And of course, it can change.
I like to make the joke that you don't have a policy for retaining envelopes in cardboard boxes; you have a policy for retaining documents that are in the envelope. Similarly, you can't have a generic one-size-fits-all legal retention policy for email, because email is just a mechanism, a way of getting information from me to you. The important question is what is that information? Is it something you need to hold, or is just an invitation to lunch? Which is something you want to keep, but most people wouldn't classify that as an important business document. Where if it was an invitation to go to lunch to talk about how you're going to get sued, then that is a real important business document.
So all of these things can add up and they can really end up creating a road block to the implementation of an email archiving solution. No matter what solution you're looking at, whether it's an in-house solution or a managed hosted solution, the critical thing is to get it up and running. You're going to have a year to pour emails into it before you have to start thinking about what you are going to delete.
So if you have any inkling at all that email archiving is going to be required for business or legal reasons, just get it running. Go out there and get a system, get it up and running and then think of getting people together and coming up with policies and making sure that the solution is meeting everyone's needs. Because the retention is really the critical thing and if you're not retaining emails, then you're exposed.
Check out the entire Email Archiving FAQ.