Why is SMTP blocked?

SMTP port 25 is blocked on all Droplets for new accounts to prevent spam and other abuses of our platform.

Dedicated email deliverability platforms are better at handling deliverability factors like IP reputation. To send mail from DigitalOcean, we recommend using SendGrid:

SendGrid delivers your transactional and marketing emails through the world’s largest cloud-based email delivery platform.

Even on older accounts where SMTP may be available, we strongly recommend against running your own mail server in favor of using a dedicated email deliverability platform.

What to do in a blackhole event when your traffic stops routing properly.
You can disable the address on your Droplet from the command line or through updating your Droplet’s eth1 interface configuration.
Ensure your Droplet’s public and private network interfaces are correctly named eth0 and eth1.