I've been having trouble receiving emails from a business contact, and I think it might have to do with the hostname being used. Specifically, the message I received showed it coming from an EC2 instance on AWS, which had a long hostname that looks a bit suspicious. I'm wondering if that IP address is dedicated and if they could request a PTR entry using one of their own subdomains to replace the AWS hostname. It seems like this might help since that subdomain is flagged in some blacklists due to its typical pattern for residential ISPs. What can they do to resolve this?
2 Answers
It sounds like the hostname isn't the main problem here. AWS blocks port 25 by default, which is often what's causing email issues. You'd need to get special permissions to unblock it, or alternatively, consider using a Network Load Balancer (NLB) that allows port 25 for inbound email.
You can't change the hostname that's automatically assigned to AWS instances, but you can definitely assign your own custom domain name to it. That might help with the email delivery issues you're seeing.
That makes sense. I know other contacts are able to receive their bills just fine, so it probably isn't just a hostname issue.