Microsoft published a white paper on the subject of “Planning for large mailboxes with Exchange 2007″ last month, and this has caused some discussion about email stubbing around the blogosphere. Admittedly an arcane topic that not many people know or care about, stubbing can actually have a big impact on your email performance–but as it turns out, it’s not as easy as all that. At its essence, stubbing is just an archiving mechanism taht strips an email of its attachments, replaces it with a stub file or link within the message, and then stores the actual attachment in an archive.

Whether or not to stub emails should be a part of the discussion when planning for email storage, simply because storage–especially for a large enterprise–can be a problem. Deleting older emails is not an option for many companies, because it might violate regulations–and that’s why you can still find a five-year-old email message about a co-worker’s retirement party still floating around somewhere. Similarly, moving emails to backup tapes or PST files can also sometimes make it difficult to find an email, or may even result in loss. Seriously, have you ever tried to get one of the IT guys to go back into that little room over by the coffee machines where they keep the backup tapes and try to find anything? Not going to happen!

The Microsoft paper takes the position that stubbing can cause some search and performance problems over time, and instead, recommends that users of Exchange use a third-party email archiving solution to move old emails out of the email boxes completely and into an archive. This seems logical: Over time, an email inbox can get quite large, with tens of thousands of emails. And if you’re not allowed to delete any of them, that many messages–even if they’re just stubs–can quickly become unmanageable. And of course, since a stub file has very little information in it-sometimes only a message header–trying to find an old message becomes almost impossible. And so the solution isn’t cut-and-dried, and the answer is, “it depends.” Smaller email systems may well benefit from taking a stubbing approach, although medium-sized and large enterprise systems would probably do better with a pure archiving solution.

Microsoft’s approach, besides applying third-party archiving, is to recommend larger email boxes for Exchange, which makes sense, because as the paper points out, the volume and size of email continues ot increase daily, and end-users who have to spend time every day trying to manage a mailbox with a low quota is not going to be productive.