Expiry headers function by embedding specific tags within the email's header section. Common tags used include Expiry-Date and x-expires. These tags inform email clients and servers about the expiration timeline. For example:
Expiry-Date: Wed, 20 Oct 2023 18:30:00 GMT
When the specified date and time are reached, email clients can treat the email as expired, potentially moving it to a different folder or flagging it as outdated.