With email being the preferred way to receive notifications, it may happen to all of us to receive emails that are not extremely relevant or which do not require immediate attention.
This, as example, can be consists of Forums or other services notifications. Some e-mail providers offer the possibility to use a technique called "email tagging" or "plus addressing"; this consist in offering a capability where the local part of the email address can contain a tag, separated by a "+". Basically, an email address like user+tag@domain would be delivered to user@domain.
From an Exchange prospective user+domain would not be resolvable as such email address would not be associated to any existing user. This sample transport agent solves this problem by removing the "+tag" from the local part of the email address in the P1 header in order to allow the correct routing to the excepted mailbox.
The same does not modify the P2 header so that the tag is exposed at the recipient and the same can be intercepted by Inbox Rules that moves the messages to separate folders.
As an examples, let's suppose a user has an email address of User@Contoso.com and there is an internal application where he can sign-up and which may send multiple notifications throughout the day; at this point he could use the e-mail address User+Notifications@Contoso.com; then he would create a new Inbox Rule in OWA/Outlook which would move items when these are sent to User+Notifications@Contoso.com.
Here some examples.
Sending an email with P1 and P2 header containing a tag.
Creating an Inbox Rule that intercepts messages sent to a given address.
Actual results as seen in OWA.
Here the actual sample agent: TaggingAgent.