Answer
This is controlled by the DEFAULT_MAIL_SENDER parameter inside the MAIL_SENDER connector configuration in the Setup IFS Connect window — the actual outgoing 'From' address used by the mail-sending mechanism is driven by this connector-level configuration, not by whatever from-address value your own PL/SQL code passes to Command_Sys.Mail. If emails are consistently showing an unexpected sender address regardless of what your code specifies, check and correct the DEFAULT_MAIL_SENDER value on the relevant Mail Sender connector rather than assuming the issue is in your own code.