In Outlook, you can add an expiration date to the email you send or receive. After the expiration date, the email will be displayed with a different formatting. Outlook's built-in tools can automatically manage expired emails.
The expiration date applies only to emails, not to calendar events or tasks, as these items have their own entries. You can use their own dates to manage them.
Set an expiration date for an email
To To add an expiration date to an e-mail sent by you, you must open the E-mail Properties window. Open the email, and then click Message> Tags.
This opens the E-mail Properties window, which you can also access through Options> More Options or File> Properties. Select the "Expires" check box and select a date and time.
Click "Close" to return to your email. There are no visible signs that an expiration date has been added, and you can send the email as normal.
To add an expiration date to an email received, open the email and click Message> Tags (or File> Properties.]
This opens the Properties window for the Email There are not as many options for a received email as there are for a sent message, but you can still set an expiration date and expiration time.
What causes an expiration date?  So you've added an expiration date to an email, which is great and all, but what's the benefit of it?
Expiration dates are used by Outlook in a variety of ways to keep you focused on what's important. Expired emails are in the Generally not as important as emails that have not yet expired Outlook automatically formats expired emails differently.
If you have set conditional formatting in Outlook, you may have two options notice the "expired elements". Formatting rule.
This rule formats any e-mail that has expired, with a gray font and the crossed out text.
Allows you to know that the email has this option expired, so you can focus on more important emails first. If you have sent an e-mail with an expiration date, this formatting will also be applied to the recipient's Outlook. Other email clients like Thunderbird or web apps like Gmail or Yahoo! Mail, ignore the date and do nothing with it.
You can also add a column to a folder that indicates the expiration date of an email. Right-click a column heading in the folder to which you want to add the column, and then click Field Chooser.
Select "Date Time Fields" from the drop-down menu, and then select "Expires."
Drag the "Expires" entry to your folder Add it to the columns.
When you open an expired email, Outlook notifies you with a message in the header.
You can post an expired email. Mail will continue to answer or forward, but Outlook will display a warning message when you try to forward it.
 Click Yes to send the e-mail or No.
Manage your email with expiration date
Some of Outlook's built-in tools also use expiration dates If you have set up AutoArchive in Outlook, you may have an option to expire expired items ( email Arrange r)
If this option is enabled, AutoArchive will be deleted or moved (depending on the other settings) all emails that have passed the date. This is a great way to automatically remove expired emails and prevent your mailbox from becoming clogged.
If you do not want your expired emails deleted or moved, but you do not want them to appear in Outlook You can set Outlook synchronization rules to prevent them from being downloaded from the Exchange email server ,
When you create a synchronization filter, click the Advanced tab, and then click the Field button.
 Select Date / Time from the menu. The field is also available in the "All Email Fields" and "All Post Fields" options.
Set "Condition" to "On or Next" and the "Value" to "Yesterday." Then click on "Add to list".
This filters all expired tasks. If they expired yesterday or earlier, they will not sync with Outlook and will not appear in your mailbox. You will still be available in the Outlook Web App if you want to see them there.
You can not set up rules to automatically add an expiration date to inbound emails or create a quick step that sets an expiration date on the press of a button, but you can automatically add an expiration date to all outgoing emails. Click File> Options> Email, scroll down to Send Messages, and check Mark emails as expired after many days.
Enter the number of days you want the messages to expire, and then click OK. This will automatically add an expiration date to all emails you send.
The expiration date is a useful way to manage your priorities and mailbox with irrelevant messages that are no longer relevant, and you can use Outlook tools to delete or hide messages that you no longer need , It's another tool in combat to keep your mailbox out of control, and this is a very useful tool.