2.    Note the output.

3.    If the connection times out, check your local firewall rules, routes, and access control lists (ACLs).

If you use an Amazon Elastic Compute Cloud (Amazon EC2) instance, check the associated instance's security groups, the subnet's network ACL, and the subnet's route table to be sure that the required rules and routes are configured. For more information, see

Note: By default, Amazon EC2 throttles traffic on SMTP port 25 for all instances. If you continue to receive timeout errors using SMTP port 25, you can request that the throttle be removed or you can change the port that is used for sending (for example, 587). For more information, see 

Example TCP connection troubleshooting

If an EC2 instance is trying to send outbound traffic on TCP port 25, 587, or 465, check the following:

• Be sure that the security group outbound (egress) rules allow traffic to the SMTP server on TCP port 25, 587, or 465. For more information, see 
  Security Group Rules.
• Be sure that the network ACL outbound (egress) rules allow traffic to the SMTP server on TCP port 25. Also be sure that network ACL inbound (ingress) rules allow traffic from the SMTP server on TCP ports 1024-65535. For more information, see Network ACL Rules.
• Be sure that the EC2 instance has internet connectivity. For more information, see Enabling Internet Access.
  

If an EC2 instance is receiving inbound traffic on TCP port 25, 587, or 465, check the following:

• Be sure that the security group inbound (ingress) rules allow traffic from SMTP clients on TCP port 25, 587, or 465.
• Be sure that the network ACL inbound (ingress) rules allow traffic to the SMTP clients on TCP port 25. Also be sure that network ACL outbound (egress) rules allow traffic to SMTP clients on TCP ports 1024-65535.
• Be sure that the EC2 instance has internet connectivity. For more information, see Enabling Internet Access.
  

Troubleshoot SSL/TLS negotiations

If you're still experiencing connectivity or timeout issues after troubleshooting the TCP connection (see the first section), check if there are issues with SSL/TLS.

1.    Run the command openssl as follows from an EC2 Linux instance launched from an Amazon Linux Amazon Machine Image (AMI).

Be sure to replace the endpoint with the Amazon SES endpoints you're using.