Hi,
This is a query with use of Outlook running under Mac OS.
Messages older than around 6 months are not visible and I can only assume some filter or rule is operating somewhere to bin older messages (unlike my gmail a/c which remain as long as I wish).
I've searched various pages online which suggest I do the following:

• Go to File > Account Settings > Account Settings.
• Chick the Exchange account you want in the Email tab, then click Change.
• Under Offline Settings, adjust the slider to change the amount of time that your mail will be stored in the offline cache.

However, it seems that Mac version of Outlook Mail has a different layout and I cannot find the Go to File > Account Settings > Account Settings options.
Any ideas please?