Check your “deleted” folder for the deleted email. If you find the one you want to restore, you can right click the email and move it to your inbox. Bear in mind this folder may be periodically purged automatically and may make some emails inaccessible.
Your best option for recovering deleted emails is a cloud-based backup system, which essentially serves as a vault that you can access when you need it, but it doesn’t clutter your inbox. With cloud-based backups like Mimecast offers, you can access any email any time.