You cannot access an external address using TCP port 25. For example, you run the
Telnet smpt.***.com 25 command, and the command execution fails.
By default, the outbound direction of TCP port 25 is blocked.
Apply to open TCP port 25 (Outbound).
Note: Before the application, you have to agree that you only use the TCP port 25 for communicating with a third-party SMTP server and deliver email messages through a third-party SMTP server. Alibaba Cloud has the right to block the TCP port 25 permanently if you use your own SMTP server to deliver email messages from the applied IP address.
Open the Open Port 25 page.
- Log on to the Alibaba Cloud console.
Hover the mouse over your account, and click Security Console on the drop-down list.
In the Security console, click Open Port 25.
On the Open Port 25 page, complete the application to open TCP port 25.
Click Apply to open Port 25.
Enter the IP and the associated domain name that you want to apply to open the TCP port 25, and click OK to add the IP.
Note: You can only apply for the ECS instances and EIPs under the Alibaba Cloud account that you log on with.
After adding the IPs and domain names, select the Agreed “Terms Governing the Use of Port TCP 25” option, and click Next.
Complete the application form, and click OK to submit the application.
Note: You may get the feedback one day after you submit the application.