Outlook allows you to add an expiration date to email you as sending or receiving. Once the expiration date has passed, the e-mail will be displayed with different formatting, and you can use Outlook's built-in tool to handle e-mail automatically.
The expiration date is for e-mails only, not calendar events or data because these items have their own dates that you can use to handle them.
How to set a due date on an email
To add a expiration date of an email you send, you must open the Email Properties window. Open the email, and then click Message> Tags.
This opens the E-mail Properties window, which you can also access by clicking Options> More options or File> Properties. Click the "Expires after" check box and choose a date and time.
Click Close to return to your email address. There will be no visible signs that an expiration date has been added and you can send the email as usual.
To add an expiration date for an email you received, open the email and click Message> Labels or File> Properties).
This opens the E-mail Properties window. There are not so many options for a received email as there is for a message you send, but you can still enter a due date and time.
What does an expiration date do?  So you have added an expiration date to an email. It's good and everything, but what's the benefit of doing it?
Exit date is used differently by Outlook to help you focus on what's important. E-mail that has expired is generally not as important as e-mails that have not expired, so Outlook automatically shapes outgoing e-mail messages differently.
If you have looked at setting up conditional formatting in Outlook, you may have tagged the "Expired Items" formatting rule.
This rule formats all e-mails that have passed their expiration date with a gray font and the text was intercepted.
This will let you know that the email has expired so that you can focus on more important emails first. If you have sent an email with an expiration date, this formatting is also used in the recipient's Outlook, but other email clients like Thunderbird or web apps like Gmail or Yahoo! Mail will ignore the date and not do anything about it.
You can also add a column to a folder showing the end date of any email. Right-click a column header in the folder you want to add the column to, then click "Field Selector".
Select "Date Time fields" from the drop-down menu and then select "
Drag and drop the" Expires "section of your folder to add it to the columns. 
When you open an expired mail, Outlook will notify you with a message in the headline.
You can still reply or forward an expired mail, but if you try to forward it, it will show
] Click "Yes" to send the e-mail, or "No" to cancel.
Use expiration date to manage your email
Some of the embedded tools in Outlook also use the expiration date. If you have set AutoArchiving in Outlook, you may have marked an option to "Delete deleted items (email folder only).".
About it here is turned on, AutoArchive will delete or move (depending on the practice rich settings) all emails where the date has passed. This is a great way to automatically delete outgoing emails and stop them from pinching your mailbox.
If you do not want your deleted emails to be deleted or moved, but you do not want to see them in Outlook either. You can set Outlook sync rules to prevent them from downloading from the Exchange email server.
When you build your sync filter, click the Advanced tab and then click the "Field" button.
 Select date / time field> Starting from the menu. The field is also available in the options "All Mailboxes" and "All Mailboxes".
Set "Terms" to "on or before" and "Value" to "yesterday" and then click "add to list".
This will filter out all deleted information so that if they ended yesterday or earlier, they will not sync with Outlook and will not appear in your mailbox. They will still be available in the Outlook web app to view them there.
You can not set rules to automatically add expiration date for incoming emails, or create a quick step for expiry date at the press of a button, but you can automatically add an expiration date for all outgoing emails. Click File> Options> Email, scroll down to send messages, and tap "Select email messages that ended after this many days."
Enter the number of days after which you want messages to expire and then click "OK." This automatically adds an expiration date for all emails you send.
Exit date is a useful way to manage your priorities and your mailbox through low-light messages that are no longer relevant and allow you to use Outlook tools to delete or hide messages that you no longer need. It is another tool in the fight to prevent your mailbox from being out of control and a very useful tool for it.