|Having too many emails in your company or personal email account can be a problem. Not only can Mail become sluggish, but nightly backups by your IT department will take longer and require more storage space. The best way to handle your email is by moving your INBOX items and your SENT items into local folders in your personal computer in Outlook or Apple mail.
Those emails will no longer exist on the server, but you'll have local copies in case you ever need to reference them. You can even place items BACK to your INBOX to reference while you are not near your computer such as on a mobile devise.
Don't forget to backup your computer too!