The SMTP Service
SMTP stands for Simple Mail Transfer Protocol and is the protocol which the majority of all mails are transferred around the Internet. For Ocean Mail Server to be able to receive mails it uses a built in SMTP server which handles and processes all incoming mail. SMTP is an essential part of Ocean Mail Server and in most circumstances should always be enabled.
The SMTP service can generally be used in 2 different ways. The first is to accept mail from the Internet, usually from other mail servers, and then deliver it to local accounts (incoming mail traffic). The second is to allow local users to use the SMTP for their outbound mail, which the mail server should deliver to the correct local or external account

Enabling the SMTP Service
Enabling SMTP is easy and can be done by enabling a single tick box. However, care should be taken to ensure the service is secure (please read the following sections). For more information on managing the listening port please view the Tutorial: Using the Listening Services page.

SMTP Security - Preventing Open Relays
It’s important that you secure your SMTP so that only you and selected users can use it to relay mails onto external accounts. Failing to so can often lead to your SMTP being abused by SPAM systems, which will eventually result in your IP being ‘black listed’. Securing your SMTP against this is simple and can be done in a variety of ways, but the most secure way is by enabling SMTP Authentication. This forces any user who wishes to have relaying access to provide valid login details (often their normal username and password). For more information on open relays please view the Tutorial: Important Security Considerations page.

SMTP Security - Preventing General Abuse
Ocean Mail Server has a variety of security options which reduce the chances of your SMTP being used by abusive users and SPAM systems. These options include facilities which detect common forms of abuse and allow you to block the abusive IPs found. This includes transfer limits per IP, tarpitting and various SPAM detection options (please read the following section). It is recommended that you try enabling some of these features and finding a solution that works best for your server.

SPAM Detection
To help prevent your users receiving unwanted SPAM mails, there are 3 filters available which can help identify and handle potential SPAM mails. The first and most powerful detection method available is the Real-time Black List (RBL) filter. This allows the mail server to verify that an incoming connection’s IP is not black listed. There are several online databases of IP black lists and Ocean Mail Server allows you to use as many RBL’s as required. The other 2 filters perform other checks that can often identify a SPAM mail.

Configuring Your Mail Client
When configuring your mail client you should ensure that the outgoing server settings are consistent with your mail server settings. If you have enabled SMTP Authentication, your mail client must be configured to 'log in' to the outgoing server. For more information on configuring your mail client you should read the Tutorial: Setting Up Your Mail Client page.