Imagine how much more time you’ll have

You have just built a new mail server for your organization that previously was using a cloud-based service. Unfortunately, you are finding that external sites are timing out when attempting to send mail to your new SMTP server. What port should you enable in your firewall to allow your mail server to properly communicate?

A) tcp/25

B) tcp/110

C) tcp/143

D) udp/161

E) Tell everyone you have a new zero-mail security policy