Definitions

There is a link called Definitions (see Figure 3.33 and Figure 3.34) to define characteristics of the e-mail server:

• Message maximum size: It's the global message maximum size of a sending/receiving message
  Value by default: unlimited.
• Maximum time to hold the message in the server: Maximum time the message will be in mail queue
  Value by default: 604800 seconds (7 days)
• Maximum number for simultaneous SMTP connections: Number of connections that the server can support
  Value by default: 20
• Incoming message timeout: Maximum time to receive a single message in server. If reached it will timeout
  Value by default: 1200 seconds
• Outgoing message timeout: Maximum time to send a single message. If reached it will timeout
  Value by default: 1200 seconds
• Reject emails from invalid domains: The server will reject incoming mail if the sender's domain MX record don't exist, so it will be invalid.
  Default value: Yes
• Reject emails from invalid servers: The server will reject incoming mail if the sender's FQDN don't have a reverse DNS record.
  Default value: No
• Approaching quota limit warning message: Message to send to the user when the mail quota is approaching the limit. The default is Quota Warning!;
• SPF (Sender Policy Framework): It's disabled by default. If active, for each incoming mail, the sender will be asked about the mail authenticity. The mail rejection will depend of the sender answer and protection level defined here. The SPF mechanisms, qualifiers and modifiers can be found at SPF site (http://www.openspf.org/SPF_Record_Syntax).
  

  These are the protection levels defined at IPBrick mail server:

  • Standard protection: The mails will be rejected if the answer is Fail;
  • Medium protection: The mails will be rejected if the answer is Fail or SoftFail;
  • High protection: The mails will be rejected if the answer is Fail, SoftFail or Neutral;
• Blacklist (RBL): Enable or disable the RBL (Realtime blacklist) or DNSBL verification. That verification is made to all incoming mails from the Internet and before the KAV filter. The following are used by default:
  • http://www.spamhaus.org/SBL
  • http://0spam.fusionzero.com
  • http://www.uceprotect.net/en
  • http://www.spamsources.fabel.dk/

Figure 3.33: E-Mail - Definitions 1/2

Figure 3.34: E-Mail - Definitions 2/2

In this interface it is even possible to define permissions of sending and receiving e-mails:

• Valid internal recipients: This list is important to fill in order to protect the server from a mailbomb attack. Here should be listed all the internal valid email addresses. If the list is empty all the internal recipients will be accepted (Figure 3.35);
• Invalid senders: A list with e-mail addresses that are not allowed to send email (Figure 3.36).

Figure 3.35: E-Mail - Definitions - Valid internal recipients

Figure 3.36: E-Mail - Definitions - Invalid senders