RBLs and URIBLs
Real-time Blackhole lists, or remote block lists, (RBLs) and URI Blacklists (URIBLs) are publicly accessible lists of known spammer IP addresses. (Though some also use domain names.) Each list is managed and maintained independently, and each has its own criteria for listing IP addresses as "spam". SmarterMail has a number of RBLs and URIBLs available by default. Therefore, system administrators have the ability to manage the default lists and enable/disable any they want to use for protecting against spam. In addition, system administrators can add their own RBLs or URIBLs as they see fit.
As these lookups can cause delays in email delivery, especially when many RBLs and/or URIBLs are being used, SmarterMail has a built-in timeout the prevents lookups from slowing down deliverys and/or causing servers to disconnect due to timing contraints. In addition, RBL/URIBL lookups are handled asychronously, further speeding up the process, and any list that doesn't return a result in 5 seconds is excluded from the lookup process.
The landing pages for both RBLs and URIBLs will display the various lists that have been added to the server. Details of each include:
- Name - The list's name.
- Average Time - The average time it takes for a result to be returned when checking the list, in milliseconds (ms). It should be noted that each check aggregates the amount of time needed for a message to be delivered. Generally, this will not be noticed by the end user. However, should a specific list take an inordinate amount of time to return a result, it could indicate that there's an issue with the list, so that particular check could be disabled until the issue is resolved to ensure the timely delivery of email.
- Timeouts - The number of times the hostname has been unavailable for spam checks. This could be due to network issues, issues with the List, etc.
- Host - The hostname of the list.
- Weight - The default weight (or range) assigned for this list.
- Spool Filtering - A checkmark appears if the list is used as part of the overall spam score assigned to a message.
- Inbound SMTP - A checkmark appears if the list (RBLs only) is being used to check messages sent TO the server.
- Outbound SMTP - A checkmark appears if the list is being used to check messages sent FROM the server.
Managing a List
Clicking on a specific list opens up a modal window. Here, system administrators can edit the list's details as needed. Depending on the list selected, the following settings are available:
- Name - The friendly name for the list that will help you and your customers identify it.
- Description - Any additional information about the list.
- Hostname - The hostname of the RBL as provided by the list moderators.
- Lookup Prefix - The is the IP address that is appended to the request sent to the RBL. For example, if you have a routed network that requires an IP address prepended to everything for it to work, that IP address should be added here.
- Enable Spool Filtering - When enabled, the weight assigned for the spam check is added to the message and used as part of its overall spam score. SmarterMail then handles the message based on the spam settings configured for a domain.
- Enable Inbound SMTP blocking - This option is used in conjunction with the SMTP Blocking settings configured in Antispam Options. When enabled, this RBL/URIBL is counted toward the weight threshold for the blocking of incoming emails.
- Enable for Outbound SMTP blocking - This option is used in conjunction with the SMTP Blocking settings configured in Antispam Options. When enabled, this RBL/URIBL is counted toward the weight threshold for the blocking of outgoing emails.
- Required Lookup Values
- IP Address - The expected IP address that's returned from the list if the sender's IP is listed with the provider. This value can be found in the setup documentation from the RBL/URIBL provider.
- Weight - The default weight for this spam check. If an email sender is listed with the spam list, this is the value that will be added to the message's total
Adding new RBLs or URIBLs
Adding a new RBL or URIBL is as simple as clicking the New button. The same modal opens as described above. System administrators simply need to fill out the relevant information in order to get the new list in the lineup. Complete documentation on how to include the list should be made available by the list provider. For example, here is the information for the SpamCop Blocking List. It clearly states the hostname to use (bl.spamcop.net) and IP that's returned (127.0.0.2). From there, system administrators simply need to fill out the other options.
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