We block several ports that are commonly abused for DDOS attacks, see the list below for reference:
- TCP: 17, 19, 1900
- UDP: 17, 19, 1900, 53413, 11211
These blocks are permanent, and cannot be removed.
The following ports may be blocked, depending on your account settings:
- TCP: 25, 137, 138, 139, 445
- UDP: 137, 138, 139, 445
SMTP over port 25
Port 25 is blocked in all G1, G2, G4 and E* regions, to prevent spam and protect the IP spaces. To send emails via servers in these regions you need to configure an external email proxy and relaying service, such as:
Additional fees may apply when using these services, after sending more emails than what's included in their respective free tier plans.
My application needs to use a local email server (like postfix), otherwise it wont work
From January 2021, all G3 plans are delivered with port 25 open. This means only approved accounts can deploy a G3 server. In order to get approved, contact support, and provide the following information:
- Describe the main purpose of your email server(s)
- Describe how you plan to secure your email server(s)
- Describe how you plan to mitigate spam
All email servers running on G3 plans, anywhere in the world must comply with the EU anti spam laws regarding emails.
Currently no exceptions are made for port blocking. This is however subject for change in the future, once we are able to fully ensure that no abuse can be performed after granting access to certain ports for individual accounts.