Many users have a very straight-forward retention policy: KEEP ALL THE EMAILS. Which is great and in theory should be just fine. In the real world, it isn’t. The simple solution is to split the emails into several differing PST files – but if outlook is already struggling under the load, that can be a lengthy and painful process.
Happily, there are tools to help. PST File Splitter does what it says on the label – breaks up one monolithic PST into several smaller ones. There’s also a paid, pro version that does more stuff.
Mailscavator is another tool, completely free, that will split PST files and allows simple filtering. Awesome!