Help Center > > FAQs> Network Configurations> EIP FAQs> Why Is Outbound Access Through TCP Port 25 Restricted?

Why Is Outbound Access Through TCP Port 25 Restricted?

Updated at: Jan 26, 2021 GMT+08:00


You cannot access an external address using TCP port 25. For example, you cannot run the Telnet smtp.***.com 25 command.


By default, TCP port 25 is disabled in the outbound direction for security purposes.

You do not need to enable TCP port 25, unless you want to deploy an email service on the cloud.

This section applies only to the AP-Hong-Kong region.


  • Use port 465 supported by the third-party email service provider.
  • Apply for enabling TCP port 25 in the outbound direction.

    If you must enable TCP port 25 on the ECS for external communications, submit an application.

Before sending the application, you must agree and guarantee that TCP port 25 is only used to connect to third-party Simple Mail Transfer Protocol (SMTP) servers and that emails are sent using the third-party SMTP servers. If you use the EIP specified in the service ticket to directly send emails over SMTP, we will permanently disable TCP port 25 and you will no longer be able to use it or request for it to be enabled.

  1. On the Create Service Ticket page, choose Products > Elastic Cloud Server.

    For details about how to submit a service ticket, see Submitting a Service Ticket.

  2. Click Open Port 25 under Select Subtype and click Create Service Ticket.
    Figure 1 Creating a service ticket
  3. On the displayed page, enter the required information.

Did you find this page helpful?

Submit successfully!

Thank you for your feedback. Your feedback helps make our documentation better.

Failed to submit the feedback. Please try again later.

Which of the following issues have you encountered?

Please complete at least one feedback item.

Content most length 200 character

Content is empty.

OK Cancel