How to remove the restriction on port 25 from my AWS Lightsail instance?

Question

How do I remove the restriction on port 25 from my Lightsail instance?

When using a Lightsail instance,  you may find that port 25 is blocked, which doesn't allow your email to function. 

Answer

You will need to reach out to AWS to lift the restriction. Please refer to Amazon's documentation on how to do this:

How do I remove the restriction on port 25 from my Lightsail instance?

Additional Information

Many providers block port 25 by default to prevent spam from being sent on their network:

Why is port 25 blocked?