MsgGetSender()

Returns the reverse path routing field of the current message – directly analogous to the return path of the SMTP envelope. Note, this is not the same as the Sender: or From: fields of the message header.

address := MsgGetSender()

address

The message sender

Send message to 'suspect junk' mailbox if sender contains the string "cyberpromo"

If(WildcardMatch(MsgGetSender(), "*cyberpromo*"),
  Do(
    SetHeader("X-Rcpts", MsgGetRcpts()),
    MsgSetRcpts(AddressOf("junk"))
  )