To be able to send outgoing email, first a valid user needs to be added to the filter cluster. This can be done from the web interface. By default the following port are available for the outgoing service: default recommended port 587 (supports STARTTLS/SSL). The outgoing service listens by default on all IPv4 addresses activated on the server.
Create a separate outgoing user on the filtering cluster for each end-user to relay outgoing email and use an "automatic user locking" to automatically close the account in case abuse is detected. There are two methods you can make per-user authentication to work - The first method is to instruct all end-users to authenticate directly to the filter cluster for their outgoing emails or in the second method, configure your current outgoing SMTP server so that it authenticates each end-user separately to the filter cluster for all outgoing emails. If you choose the second method, how easily you can configure your SMTP server depends on the SMTP software.
While using per-user authentication for outgoing mails, ensure to set the limits correctly based on the usage of the end-user and enable automatic locking.
If you find using the per-user authentication method for outgoing mails too cumbersome to set up, the other alternative is to use smarthost setup. In this method, you add a single outgoing account either based on IP or username/password in the filtering server and point all outgoing emails to this server, thus using the filtering cluster as smarthost. Most email servers have 'smart host setting' feature with which you can easily accomplish the task of configuring outgoing email filtering. Make sure to disable the 'automatic locking' setting to prevent the full server account getting locked even if one end-user sends out spam email. Also ensure to enable 'block spam' so that individual spam messages will be blocked and the administrator notified.
While using smarthosting setup for outgoing mail filtering, ensure to set the limits correctly per user based on the server.
In the 'Outgoing' area of the Manage Domain section, you can clear outgoing cache, search for outgoing email messages, set a user account for spam checking.
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