Connection Timeout - while sending email from ec2 linux sendmail

There are a few things that could be causing this issue. One possibility is that port 25, which is the default port for sendmail, is blocked by your network or the network of the server that you are trying to connect to. This could be because of a security measure or because of a network configuration issue.

Another possibility is that there is an issue with the sendmail configuration on your EC2 instance. It's worth checking the sendmail configuration files to make sure that everything is set up correctly and that there are no errors or issues.

AWS recommends using their Simple Email Service (SES) to send email from EC2 instances. SES is a managed service that makes it easy to send email from your applications. It includes features like email sending and receiving, email address verification, and feedback loops for handling bounces and complaints. If you are able to use SES, it may be a simpler and more reliable solution for sending email from your website's contact form.

AWS blocks outbound traffic on port 25 of all EC2 instances by default. If you want to send outbound traffic on port 25, you can request for this restriction to be removed by following these instructions: https://aws.amazon.com/premiumsupport/knowledge-center/ec2-port-25-throttle/

However, using SES is the recommended best practice.