I have a potential security issue where existing users (may not be himself) when they telnet to SMTP (user1@domain.com) can email to any users in the domain (*@domain.com) this can lead to someone send mail as CEO to all employees.
Connected to email.domain.com.
Escape character is '^]'.
220 EXCHANGE-CAS.ad.domain.com Microsoft ESMTP MAIL Service ready at Mon, 14 Apr 2014 13:34:20 -0400
helo localhost
250 EXCHANGE-CAS.ad.domain.com Hello [xx.xx.xx.xx]
mail from: ceo@domain.com
250 2.1.0 Sender OK
rcpt to: userx@prolifics.com
250 2.1.5 Recipient OK
Data
I fire you.
250 2.6.0 <966610a9-5d36-4bb0-9b2c-157d8ff40bfc@EXCHANGECAS.ad.domain.com> [InternalId=14418205212971, Hostname=MBOX01.ad.domain.com] Queued mail for