Why does confUSERDB_SPEC work when tested with telnet but does not when mail command is used?

Issue

• Why does confUSERDB_SPEC work when tested with telnet but does not when mail command is used?
• /etc/mail/userdb has contains following lines:

root:mailname   test@example.com
test:maildrop   root

• When an email is sent through mail command, sender address does not get rewritten to test@example.com, when telnet is used sender address correctly appears as test@example.com at the recipient's end.