Unblocking Port 25
Last updated:2026-01-26 16:49:34
Operation Scenarios
To improve email sending on Tencent Cloud IP addresses and for security reasons, access to the external TCP port 25 from Cloud Virtual Machine (CVM) instances is blocked by default. If your business scenario requires access to TCP port 25 from CVM instances (such as building email services), you can see this document for instructions to apply for unblocking the port.
Notes
It only supports unblocking of prepaid annual or monthly CVMs and currently does not support CVMs operating on a pay-as-you-go basis.
Make sure that you only use port 25 to connect to a third-party SMTP server for sending email. If you use your CVMs to send email directly, we reserve the right to permanently ban you from opening port 25.
It is recommended to prioritize the use of other ports for sending emails. For configuration guidance, see Sending Emails via Port 465.
Directions
1. Log in to the Tencent Cloud console.
2. Click your account name in the upper-right corner. Select Security Management.
3. In the left sidebar, click Unblock port 25 to go to the Unblock port 25 page.
4. Click Apply for unblocking port 25 to bring up the Apply for unblocking port 25 window.
5. In the Application for Unblocking TCP Port 25 pop-up window, you can select the region and the CVM instance for which port 25 needs to be unblocked, input details of the intended use, and set Reverse DNS (rDNS) records. Then, select I have read and accepted "Port 25 Protocol". For details, see the following figure.
6. Click OK to complete the application. Please patiently await the platform administrator to process. You can check the approval results and causes via Moderation Status on the page.
Was this page helpful?
You can also Contact Sales or Submit a Ticket for help.
Yes
No
Feedback