Why is port 25 blocked for EC2 and Lambda services?

Question

The following link is helpful in answering how to unblock port 25:
[Remove port 25 restriction from your EC2 instance | AWS re:Post](https://repost.aws/knowledge-center/ec2-port-25-throttle). However, my question pertains as to why it's blocked.

Doing some research I've found a list of reasons as to why port 25 might be blocked or throttled by hosts and ISPs, but I was hoping for a more official explanation from AWS as to why it's blocked here.

Thank you.

Brettski-AWS · Accepted Answer

Easy answer: Spam is a big problem on the internet. Blocking outbound TCP/25 connections unless customers explicitly enable it (for EC2) helps to cut down on that problem.

Thulasiram Toorpu · Answer

this is answered here.. https://repost.aws/knowledge-center/ec2-port-25-throttle

Why is port 25 blocked for EC2 and Lambda services?

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