Relocated Mapping
The optional relocated file provides the information that is used in "user has moved to new_location" bounce messages.

Table lookups are case insensitive.

The "Maps to..." field specifies contact information such as an email address, or perhaps a street address or telephone number. It's one of the following:

ADDRESS EXTENSION: When the search fails, and the address localpart contains the optional recipient delimiter (e.g., user+foo@domain), the search is repeated for the unextended address (e.g. user@domain).