Roughly speaking, the cache memory can be compared to the storage area of a desk, where the most important working material is stored for quick access. If the materials are no longer needed, they are put away to free up space again. However, if you don’t tidy up your desk regularly, you will eventually suffer from a lack of space and lose track of everything. Convenient and quick access to permanently required working materials then no longer works.
It’s a similar process on the computer. Normally, the Outlook cache is cleared regularly, so that temporarily storedfiles do not remain on the hard disk permanently and disappear through automated deletion procedures. However, this does not always work. For example, if you have opened an attachment (such as images, documents, or pdf files) and close Outlook first, the data may permanently be stuck in the cache.