The mailAddress is a Unicode string that
MUST meet the requirements of an addr-spec, as specified in [RFC2822]
section 3.4.1. This includes being in the form local-part@domain.
A directory server that is sending an update request via the
DRS Protocol Extensions for SMTP determines the appropriate email To address
field by querying the value of this attribute for the destination computer's
Server object. The directory server sets the From address field by querying the
value of this attribute for its own Server object.