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Relay Server

Operate all kind of settings when connect SMTP with the mail relay source server. You can set the number of simultaneous connections, reception interval, reception size and connection IP.

Setting the relay server

  1. Login to management console and click the server composition tab.

  2. Click the server composition on the server configuration list.

  3. Server settings dialog will be displayed.

  4. Click the relay server settings menu.

    relay server settings

  5. Following items will be displayed

    Item Required Description
    Port Yes The port number that accepts SMTP connections. This value cannot be changed.
    Max sessions Yes Input the maximum number of simultaneous SMTP session connections that can be accepted. Specify in the range of 1-100.
    Receiving interval Yes Input the interval (processing time per mail) for receiving mail from the mail relay source server in milliseconds. Specify in the range of 10-10000.
    Receiving size limit Yes Input the content size of the received email in KByte units.
    SMTP AUTH Yes Specify whether to use SMTP authentication with the mail relay source server. The account used for SMTP authentication is set in API User.
    Mechanism (Authentication method) No Specifies the authentication method for SMTP authentication.
    Authentication Method Yes Select from the following pull-down.
    Allow connections using either permitted networks or SMTP authentication
    Allow connections using permitted networks
    and optionally use SMTP authentication
    Allow connections using both permitted netrowks and SMTP authentication
    Acceptable network No Input the connection IP that allows SMTP connections. This setting is not required if you allow the connection only by SMTP authentication.
    CIDR Notation is not available.

  6. Settings will be saved in management console when clicking the save button.

About "SMTP authentication"

Using "SMTP AUTH," it is possible to record and reference connection logs for each API user in the "Operation Log" menu on Customers Mail Cloud by performing SMTP authentication for each API user.

About "Authentication Method"

Authentication Method” allows you to change the relationship between ‘SMTP Authentication’ and ‘Acceptable network’ settings.

The options for “Authentication Method” are as follows

  • Allow connections using either permitted networks or SMTP authentication
    Authenticate connections using either the allow Acceptable network or SMTP authentication (OR condition).
    SMTP relay is allowed if either of the following conditions is met: the connection is from an IP address configured for the Acceptable network or SMTP authentication is successful.

  • Allow connections using permitted networks and optionally use SMTP authentication
    Authenticate first with the Acceptable network, followed by SMTP authentication if SMTP authentication has been properly configured.
    If SMTP authentication is not specified or SMTP authentication fails, SMTP relay will still run as long as the Acceptable network is authenticated.
    (If “Avoid connection from other than acceptable network when SMTP-AUTH is used.” was set to “Avoid” prior to 9/26/2024, this option will be selected.)

  • Allow connections using both permitted netrowks and SMTP authentication
    If the connection is from an IP address configured for the Acceptable network and SMTP authentication is successful, the SMTP relay will be allowed,

When "SMTP AUTH" is not used, only connections from IP addresses set to the allowed network will be accepted.

If neither “SMTP Authentication” nor “Acceptable Network” is set, mail cannot be sent.

Receive flow control

You can control the flow of mail received by the mail server using the maximum number of connections and the reception interval. Customers Mail Cloud causes an SMTP transaction to wait until the millisecond specified in the receive interval is reached after receiving one mail.

The received flow rate is calculated by the following formula.

[Email flow rate per hour] = (3,600,000 ms / [Reception interval ms]) * [Number of sessions] * [Number of IP]

The number of sessions = 30 and the reception interval = 360 are defalult values, they can be changed.

Reception performance can be scaled out by assigning multiple IPs.

The number of sessions=30 and the reception interval = 360.

The number of IPs is automatically adjusted to handle mail traffic properly.

Note

For example, if you want to limit the mail flow to 100,000 mails/hour, specify the maximum number of connections=10, and the reception interval=360. With this setting, the set value of mail flow will occur when the mail relay source server connects 10 SMTP sessions in parallel and sends mail continuously. If the number of parallel mail relay source servers is 5, the maximum number of connections=5 and the reception interval=180.

Warning

For emails with large content such as attachments, the SMTP transaction may not end within the reception interval. In this case, the calculated mail flow rate does not come out. If you want to increase the flow rate of mail per hour, instead of setting the reception interval extremely short, Increase the number of sessions (=increase the degree of parallelism).

Reception size control

The content size of the mail received from the mail relay source server has the following restrictions to protect the memory resources of the mail server.

Maximum settable reception size = 786,432KB (768MB) / Number of sessions

Note

If the reception size is 20,480KB (20MB), the maximum number of sessions that can be set is 38.

In the Standard plan, the reception size is set to 20,480KB (20MB).

Saving the settings

The settings will be saved when the Save button is clicked or when the screen transitions to another setting screen (menu click, next button click, etc.) are saved.

Reflection the settings

This will be enabled when the saved settings reflected in mail server.After saving all the settings including other settings in the management console please do reflect settings in the mail server.