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 globally blocked in all regions to prevent spam and protect the shared IP space. To send emails from any of your server, you need to use a email proxy/relay service such as one of these:

Additional fees may apply when using above 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

Above services can be configured as a proxy or relay for email traffic sent to and from your local mail server if running postfix or similar. Tutorials can be fount on each service own website.


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.

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