You can also check the Include items with “Do not AutoArchive” checked box.
Under Archive items older than option, choose the Data Range.
You can also opt for the entire mailbox to archive.
Now, in the Archive this folder and all subfolders option, choose the folder you want to archive.
Select Tools from the left panel and select Clean Up old items.
Here are the steps to archive items in Outlook 2016, 2019, and 2021. You can archive old or unwanted items to reduce the mailbox (OST) size. Here are some ways to reduce the size of large Outlook data files. To avoid and resolve Outlook pauses and other issues due to large data file, the best solution is to reduce the file size.