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Blocked ports
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Blocked ports

To secure the Selectel infrastructure from malicious network activity, access to some TCP/UDP ports is restricted.

Inbound and outbound traffic is blocked at the moment of passing Border Routers (border routers) at the edge of the Selectel Internet network. For TCP port 25, only outgoing traffic is blocked.

UDP portsTCP portsTCP/UDP ports
Blocked ports17, 111, 427, 389, 520, 1900, 3702, 1121125 (outbound traffic)135, 137, 138, 139, 139, 445
Can be unblockedCan be unblocked for the public dedicated subnet of a dedicated server and the public subnet of a cloud server. To unblock , create a request to unblock 25 TCP portCan be unblocked for the public dedicated subnet of a dedicated server and the public subnet of a cloud server. To unlock create a ticket

If the port does not fall under the above restrictions, check its availability on the OS side using the Nmap utility.

Mailings

To prevent unauthorized mailings, TCP port 25 is blocked for outgoing connections towards public IPv4 and IPv6 addresses. Alternatively, we recommend using Selectel mail service, as well as mail connections on TCP ports 587 and 465 or mail messaging services:

For details on how to configure mail sending via SSMTP, refer to Configuring Mail Sending via SSMTP.

If you need to send mail directly, and Selectel mail service or other mail sending services are not suitable for you, you can create a request to unblock 25 TCP port.

Create a request to unblock 25 TCP port for account

Each application will be reviewed individually, unlocking is not guaranteed.

The unlock applies to public dedicated subnets of dedicated servers and public subnets of cloud servers in the account. For addresses with the /32 prefix from a shared subnet, port 25 will remain closed.

  1. Make sure you have a dedicated subnet to which you can move your mail servers:

  2. If a dedicated subnet is not available, order one.

  3. Create a ticket requesting to unblock port 25.

  4. Wait for technical support to reply that port 25 has been unblocked for your account.

  5. Move your mail servers to a dedicated subnet.