Answer: sdr

AnswerCrossword Clue
SDRE-mail writer, e.g. (abbr.)
SDRTransmitter: Abbr.
SDRE-mail writer: Abbr.
SDRE-mail correspondent: Abbr.
SDRDispatcher: Abbr.
SDRUser of mails: Abbr.
SDROne who transmits: Abbr.
SDRLtr. mailer