What Should I Do If Emails Configured on an ECS Cannot Be Sent?

Solution

• For the emails sent using the browser:

  When you use a browser to log in to your mailbox, HTTP is used, and the default port number is 80. However, SMTP is used between email servers.

  If you use a browser to send emails, enable port 80 for TCP in the outbound direction.

  1. On the ECS details page, locate the security group and click the security group ID.
  2. On the Security Group page, click the Outbound tab and then Add Rule.
  3. In the dialog box that is displayed, set Protocol/Application to TCP and Port to 80. Then, click OK.
     Figure 1 Adding port 80
     

• For the emails sent and received through an email client:

  The protocols used on the receiving and transmitting ends are different.

  Protocol used on the transmitting end:

  SMTPS is used, and the port number is 465. Alternatively, SMTP is used, and the port number is 25.

  Port 465 is recommended. If port 25 is required, enable it. For details, see Related Operations (Requesting for Permitting TCP Port 25 for Outbound Transmission).

  Protocol used on the receiving end: POP3 is used, and the port number is 110.

  For details, see steps 1 to 3.

  

  Add an inbound rule with Protocol set to TCP and Port to 110. Add an outbound rule with Protocol set to TCP and Port to 465 or 25.

Related Operations (Requesting for Permitting TCP Port 25 for Outbound Transmission)

TCP port 25 is prohibited by default in the outbound direction for security purposes. This configuration affects your service running only if your email service is deployed on the cloud.

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.

1. On the Create Service Ticket page, choose Products > Elastic Cloud Server.
2. 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.