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## Configuring Mail Services

Your control panel works in cooperation with your mail server, which provides mail services for your domains. After installation the mail server is configured automatically and is ready to serve, however, we recommend that you review the default settings to make sure that they satisfy your needs:

1. Go to Server > Mail. The server-wide mail preferences screen will open on the Preferences tab.
2. If you wish to limit the size of an e-mail message that can be sent through your server, type the desired value in kilobytes into the Maximum letter size box, otherwise, leave this field blank.
3. If you wish to protect your users from dictionary attacks by not allowing them to use simple passwords, select the Check the passwords for mailboxes in the dictionary option.

   A dictionary attack is when someone tries to find out a valid user name and password by running a program that tries different combinations of dictionary words in different languages. Dictionary attacks can be successful because many users choose their passwords carelessly.

   Note. In order for this option to work you need to make sure that the Password must meet complexity requirements option is switched on in your server's Local Security Policy settings (the option is located in Start > Administrative Tools > Local Security Policy > Account Polices > Password policy).

4. If you wish to use an additional SMTP port with mandatory authorization for e-mail message submission, select the Switch on message submission check box and choose the IP address on which the port will be working. Note that availability of this option depends on the mail server you're using.
5. Select the mail relay mode.

   With closed relay the mail server will accept only e-mail addressed to the users who have mailboxes on this server. Your customers will not be able to send any mail through your outgoing SMTP server, therefore, we do not recommend closing mail relay.

   With relay after authorization, only your customers will be able to receive and send e-mail through your mail server. We recommend that you leave the authorization is required option selected, and specify allowed authentication methods:

   - POP3 authorization. With POP3 authorization, once a user has successfully authenticated to the POP server, he or she is permitted to receive and send e-mail through the mail server for the next 20 minutes (default value). You can adjust this interval by specifying another value in the lock time box.
   - SMTP authorization. With SMTP authorization, your mail server requires authorization if the e-mail message must be sent to an external address.

   If you do not wish to use relay restrictions for networks that you trust, specify the network IP and mask in the Use no relay restrictions for the following networks: field (e.g., 123.123.123.123/16) and click the icon. To remove a network from the list, click the icon corresponding to the network you wish to remove.

   The relay hosts on the networks in the list are considered not to be potentially operated by spammers, open relays, or open proxies. A trusted host could conceivably relay spam, but will not originate it, and will not forge header data. DNS blacklist checks will never query for hosts on these networks.

6. Select the Enable support for Trend Micro RBL+ Service checkbox to enable the mail abuse prevention system to help you defend your customers from abuse by spammers, and enter the DNS zone name (e.g. domain.com) in the MAPS zones field. You can specify several MAPS zones separated by semicolons.
7. Click OK to submit any changes.

In this section: Setting Up Spam Protection Setting Up Virus Protection