I was on-site with one of my business computer clients last month who had a question for me. They wanted to know why his Microsoft Outlook email was slow. Other tasks were on the agenda and as I worked through their requests I looked at their Outlook folders and settings.
Some of their email folders had thousands of messages in them. The Sent folder contained 6000 messages and another one had 3000. My general advice for email users is the more messages in your folders, the more chance of problems. I suggested my client clean out the unneeded messages and save the important ones. If needed, we could save the messages as a file or archive a portion of his email.
Once this was done, his Outlook email opened faster and didn’t hang when he sends messages.
An interesting note is the deleted folder or trash does not empty itself automatically by default. You have to manually empty it and I have seen some folders with many thousands of messages. The user thought the messages were automatically deleted but the weren’t.