LPIC-2 Certified Linux Engineer (202-450) (#30)

It has been discovered that the company mail server is configured as an open relay. Which of the following actions would help prevent the mail server from being used as an open relay while maintaining the possibility to receive company mails? (Choose two.)

Restrict Postfix to only accept e-mail for domains hosted on this server
Configure Dovecot to support IMAP connectivity
Configure netfilter to not permit port 25 traffic on the public network
Restrict Postfix to only relay outbound SMTP from the internal network
Upgrade the mailbox format from mbox to maildir