What are the best practices to set up an email server on my EC2 Linux instance?

Resolution

Use the following best practices to set up your email server on an EC2 instance:

• By default, AWS restricts outbound traffic on SMTP port 25. Request to have the restriction on port 25 removed from your EC2 instance. The restriction is specific to AWS Regions. Submit a separate request for each Region. For more information, see How do I remove the restriction on port 25 from my Amazon EC2 instance or AWS Lambda function?
• Assign an Elastic IP address to your EC2 instance that hosts your email server.
• To make sure that your outbound emails aren't marked as spam, set up reverse DNS. For more information, see Configurable reverse DNS for Amazon EC2 Elastic IP addresses.
• Make sure that you aren't in violation of the AWS Acceptable Use Policy. If you violate the AWS Acceptable Use Policy, then AWS blocks ports that you use to send email. The AWS Abuse team sends you an email notification that contains mitigation steps to remove email port blockages. For more information, see What do I do when I receive an abuse report from AWS about my resources?
• Use Amazon Simple Email Service (Amazon SES) to externally relay your emails. Amazon SES provides an SMTP endpoint to send your emails so that you don't have to send email from your EC2 instances. Email providers might block cloud IP address ranges. This might prevent the delivery of emails that you send directly from your instances.
  Note: AWS enforces default limits on the number of emails that you send from individual accounts. For more information, see Managing your Amazon SES sending limits.