2.1.1 sender Field

Within the sender field, the reverse-path field MUST be set to the email address of the sender of the original message. The reverse-path field MUST be formatted as one of the following:

• A Simple Mail Transfer Protocol (SMTP) email address, as specified in [RFC2821].

• A distinguished name (DN) address formatted according to the following ABNF notation. The format for x500-dn is specified in [MS-OXOABK] section 2.2.1.1.

  <distinguished-name-address> = "[EX:" x500-dn "]"