Definition

Alternate RFC 822 email address of this recipient. If the MTA receives mail with a “to” header with this email address, it rewrites the header with the value of the mail attribute and routes the email to that inbox. The reverse-pointing addresses are rewritten from the value of any of a user's mailAlternateAddress attributes to the value of the user's mail attribute. (That is, the MTA will rewrite the following headers, if they match this attribute, to the value of the user's mail attribute.)

The mailEquivalentAddress attribute works similarly to route the email, but does not rewrite the header.

The local part of the address may be omitted to designate a user/group as the catchall address. A catchall domain address is an address that will receive mail to a specified domain if the MTA does not find an exact user address match with that domain.

This attribute, along with mail, are the default attributes used for reverse searches.