An Amazon EC2 instance is unable to connect an SMTP server in a different subnet. Other instances are successfully communicating with the SMTP server, however VPC Flow Logs have been enabled on the SMTP server's network interface and show the following information: 2 223342798652 eni-abe77dab 10.1.1.200 10.100.1.10 1123 25 17 70 48252 1515534437 1515535037 REJECT OK What can be done to correct this problem?
A) Add the instance to the security group for the SMTP server and ensure that is permitted to communicate over TCP port 25.
B) Disable the iptables service on the SMTP server so that the instance can properly communicate over the network.
C) Install an email client on the instance to ensure that it communicates correctly on TCP port 25 to the SMTP server.
D) Add a rule to the security group for the instance to explicitly permit TCP port 25 outbound to any address.

Question

Quizplus · Accepted Answer

The security group for the instance does not allow outbound TCP port 25 traffic to any address. Adding a rule to the security group to explicitly permit TCP port 25 outbound to any address will resolve the issue.

An Amazon EC2 Instance Is Unable to Connect an SMTP