A company is migrating its exchange server from its on-premises location to a VPC in the AWS Cloud.
Users working from home connect using a secure, encrypted channel over the internet to the exchange server. However, after the migration to AWS, users are having trouble receiving email.
The VPC flow log records display the following.

What is the root cause of the problem?

A. SMTP traffic from the network interface was blocked by an outbound network ACL.
B. SMTP traffic from the network interface was blocked by an outbound security group.
C. SMTP traffic to the network interface was blocked by an inbound network ACL.
D. SMTP traffic to the network interface was blocked by an inbound security group.