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What ports are blocked

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 E11 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:

  • Mailgun
  • Sendgrid
  • Mailchimp

For G3 server instances you can choose the option "Enable SMTP" to deploy a server instance with port 25 open, please note that for on demand servers, reserved for a shorter period of time than 3 months additional fees will be applied as a "SMTP subscription".


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.