One giant PST for ten years of mail is a problem that keeps coming back. Splitting by year is the boring discipline that ends it for good.
Raising the limit buys time; splitting is what spends that time well. The idea is simple: your working PST holds only recent mail, and each finished year moves into its own archive PST - Archive-2022.pst, Archive-2023.pst and so on. Every file stays small, fast and easy to back up, and if one file ever does corrupt, you lose access to one year while you repair it - not to everything.
Go to File - Account Settings - Data Files - Add, create a new Outlook Data File and name it by year, stored in the same folder as your main PST. It appears in the folder pane immediately. Decide the rule now and write it down: for example, on the first working day of January, everything from the year before last moves out of the live file. A rule you repeat beats a heroic cleanup you postpone.
For bulk moves use File - Tools - Clean Up Old Items (in older Outlook, File - Archive): choose the folders, set 'Archive items older than' to 1 January of the year you are closing, and point it at that year's PST. It moves - not copies - Inbox, Sent Items and Calendar together, keeping folder structure. For a handful of folders, dragging them onto the archive file in the folder pane does the same job by hand. Let it finish without interruption; moving tens of thousands of items takes a while.
File - Options - Advanced - AutoArchive Settings can run the same move automatically every few weeks into an archive file you choose. Used well it keeps the live PST permanently lean. Used carelessly it surprises people - mail 'disappears' into an archive file they forgot existed. If you switch it on, tell everyone who uses the mailbox where the archive file lives, and never let AutoArchive point at a network drive.
When a year's move is complete, right-click the archive in the folder pane and choose Close - a closed PST cannot be written to or corrupted by daily use, and Outlook starts faster with fewer files open. Back the closed file up like any important document, and reopen it any time via File - Open and Export - Open Outlook Data File. Raising the limit only moves the wall. An oversized PST opens slower, searches slower and corrupts more easily, and the repair takes longer the bigger the file gets. The registry change is a bridge that buys you time - the real cure is archiving old mail out, compacting, and keeping every PST at a sensible size. The year split is what makes that honesty painless.
The video covers the other side of the same job - raising the ceiling on the live file once the archives are split off.
Watch Full VideoYes, while the archive file is open in Outlook, search and folders work exactly as before. A closed archive is out of search until you reopen it - which is the right trade: old years are one click away, not slowing down every day.
For a personal mailbox, years are the most predictable split - every mail belongs to exactly one year. Projects work too, but projects overlap and linger; whichever you choose, one clear rule, applied consistently, is what matters.
It means the split came too late for that file or the year was exceptional. Split it further (half-years, or pull the largest folders into their own file), or simply let that one closed file be: a closed archive at rest is far lower risk than a live file at the same size - though raising its limit works too if you must keep adding to it.