Possible causes of very slow retrieval of old emails on Outlook?

Question

At work I use Outlook 2016, and I am having trouble accessing old emails in searches. When I run a search, I get a list of emails containing the search term. If I click on a recent email, it is retrieved instantly. However if I click on an email from a year or more ago, Outlook freezes and grays out for ~30 seconds. It eventually opens the old email, but it takes a while. What could be causing the delay?

Some details: I am using Exchange and Cached Exchange Mode is set to download email for the past 1 year. [In case it's useful, Account Settings are found under the File button in upper left of the Outlook top toolbar.]

Answer 1

How do you have the account configured in outlook?

Are you using Exchange? Are you using "Cached Exchange Mode"?

What period do you have set for "Download email for the past:"?

If so was the email received before this time period?

If all the above is true then its likely due to outlook retrieving the email in online mode/view.

With regards to your question in the comments "Is there any reason not to increase the period to the maximum permitted period, which is 'All' (several years)?.".

There is several factors to take into consideration, if the mailbox is reasonably small and has a low number of emails incoming / outgoing then this shouldn't be an issue.

However if the mailbox has a considerable number of emails (100K+) or is considerably large in size (20GB+ could easily cause issues...) or has a large number of sub-folders then the hardware of the computer may not necessarily be able to handle the mailbox too well without specific components (SSD for quick R/W operations, decent CPU for indexing and general task performance). We have a number of large mailboxes that we control client side by reducing the cached amount to 3 months and advise users to use OWA if they require any further than this as the performance of Office 365's OWA out performs retrieving this data locally.