Why Is Outbound Access on TCP Port 25 Blocked?
Symptom
You cannot access an external address on TCP port 25. For example, running the Telnet smtp.***.com 25 command fails.
Cause
For security reasons, TCP port 25 is disabled in the outbound direction by default.
You do not need to enable TCP port 25, unless you want to deploy an email service on the cloud.
This section applies to CN-Hong Kong only.
Solution
Before submitting your application, you must agree to 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, TCP port 25 will be permanently disabled and you can no longer use it or request it be enabled.
- On the Create Service Ticket page, choose Products > Elastic Cloud Server.
- Click Open Port 25 under Select Subtype and create a service ticket.
For details about how to submit a service ticket, see Submitting a Service Ticket.
Security FAQs
- Are the Security Group Rules Considered the Same If All Parameters Except Their Description Are the Same?
- Why Is Outbound Access on TCP Port 25 Blocked?
- How Do I Know the Instances Associated with a Security Group?
- Why Can't I Delete a Security Group?
- Can I Change the Security Group of an ECS?
- How Do I Configure a Security Group for Multi-Channel Protocols?
- Does a Modified Security Group Rule or a Network ACL Rule Take Effect Immediately for Existing Connections?
- Why Are Some Ports Inaccessible?
- Why Is Access from a Specific IP Address Still Allowed After a Network ACL Rule That Denies the Access from the IP Address Has Been Added?
- Why Do My Security Group Rules Not Take Effect?
Feedback
Was this page helpful?
Provide feedbackThank you very much for your feedback. We will continue working to improve the documentation.See the reply and handling status in My Cloud VOC.
For any further questions, feel free to contact us through the chatbot.
Chatbotmore