Spamcatcher SMTP Service

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All mail servers require an SMTP service to send and receive email.

XMission SpamCatcher is an SMTP mail feed which provides spam filtering, virus blocking, and emergency mail spool services. Intended for our customers running their own mail servers, but don't have either the technical ability or resources to install and maintain their own copy of SpamAssassin.

XMission uses a combination of internal and external RBLs (IP and URI), a cluster of SpamAssassin servers running a large custom ruleset, and the ClamAV virus scanner to keep our customers safe. SpamCatcher “applies” these filters and processes to a customer's external mail server environment.

SpamCatcher covers you in the case of an unexpected outage by queuing your mail for up to 8 days. Providing ample time to repair your mail server without losing critical customer messaging.

Sales Information

Product page for SpamCatcher - $15/mo per domain and can be ordered online or by contacting XMission sales.

How XMission SpamCatcher Works

SpamCatcher service works by making XMission's incoming mail servers the customer's incoming mail servers. With the customer domain MX record pointed to XMission, we receive the mail and our incoming servers apply the spam filtering by using the same RBLs, virus scanning, attachment blocking, and spam scoring that they do for any other XMission email.

Once the message has been processed and received, it is relayed to XMission's email queuing server which relays the message to our customer's mail server.

Pre-emptive Blocking

SpamCatcher can be configured to delete mail at a particular score on the customer's behalf. It is typical for customers to use the provided SpamAssassin headers to filter mail as they see fit.

For example, Zimbra mail server software will filter everything that has "X-Spam-Flag: YES" into the "Junk" folder by default.

To set a custom discard score for your mail server, please contact XMission support.

Easy DNS Handling

In addition to the filtering, this service provides customers the ability to change their mail server without having to deal with DNS updates. It also keeps the customer's mail server “hidden” from the world. Customer mail servers will only see SMTP conversations from XMission's network, and can apply appropriate firewall rules.

Disable default spam tools

It is highly recommended you disable any spam scanning that is included in your own mail server when using SpamCatcher to avoid any conflicts. Should you choose to run your own spam scanning software, be sure you allow XMission's IP range (, and Additionally, if your mail server uses SpamAssassin, you *MUST* disable this, as it will prevent XMission's SpamCatcher service from functioning properly.

Example: Zimbra mail servers include SpamAssassin by default. If you run Zimbra for your mail server, be certain to disable the SpamAssassin service.

Configuring SpamCatcher

Please note: You must first activate the SpamCatcher service with XMission before applying these settings to avoid missing any email.

To configure SpamCatcher the following steps are required:

  1. Point your domain MX record to “
  2. Provide XMission support with the Static IP address of your mail server.

Once this information has been updated in the XMission mail system and to your DNS, it will begin working. Total time with XMission is approximately 15 minutes. Your domain name DNS propagation may take longer.

Clearing Mail Queue

If a customer's mail gets queued, they point their mail servers to and send the ESMTP ETRN command. When their mail server issues that command it will flush all queued mail for their domain to the mail server at the specified IP address.

XMission Spam and Virus Filtering Explained

For a deeper understanding how XMission's spam and virus filtering works, please reference this article on our blog: