Spam Filter for Outbound Email

Not every spam filtering solution comes with an outbound spam filter by default. An outbound spam filter is a crucial consideration when evaluating any anti spam solution as it stops your IP address being blacklisted by mistake.

How does your IP address become blacklisted? Easily. An email with a misspelled title or the repeated spam-related keywords or characters (“!” or “$” for example) could be identified as spam by an overzealous spam filter. If enough overzealous spam filters report your IP address as a source of spam, it could get placed on a global blacklist.

The global blacklist is shared between all reputable spam filtering service suppliers. This means that all your group’s emails would be caught by their recipients´ email filters, and only sent to your inbox once your organization’s name had been added to a whitelist – or removed from the global blacklist.

Additionally If your email server and your website share the same IP address, access to your website could be restricted by web filters using the same global blacklist. If you rely on your website for attracting leads or Internet transactions, the consequences to your businesses of being blacklisted could be significant.

Deleting your IP address from a global blacklist is not difficult, but it can be time-consuming. All the time your group’s IP address is blacklisted, the flow of communication between your organization and its customers is slowed – potentially damaging your organization’s profitability.

How to Review Your IP Reputation

  • Your “IP reputation” is a contributing factor towards whether your emails are labelled as spam.
  • There are some online resources you can use to find out if your IP address has a good, neutral or poor reputation.
  • Once you have conducted a test, you will be in a better position to determine whether or not an outbound spam filter is required.

The blacklisting of your group’s IP address may have occurred due to a perfectly safe email, or there may be more sinister reasons for it. Possibly an employee within your group is using his or her corporate email address to send out bulk email for their own financial profit.

This is not only an abuse of their email rights, but could also reflect badly on your group. If word was to circulate that your organization authorized – or failed to address – the use of its email for spam, that would not only harm your group’s profitability, but also its credibility.

Another reason why your group’s IP address may be added to a global blacklist is if an outbound email is found to include malware. The malware may not have come from your network, but could be within an attachment prepared by a staff member on his or her malware-infested home computer.

An outbound spam filter will prevent all these potential scenarios from taking place. It scans all outbound emails for both spam and malware, and blocks any that may lead to your organization’s IP address from being blacklisted. The reports gathered by your spam filtering solution will alert you to any emails held in quarantine awaiting your action.

Every spam filtering solution compares the IP addresses of inbound emails against a Realtime Blackhole List. A Realtime Blackhole List is another label for a global blacklist of known spammers and is updated as new sources of spam are discovered.

However, this is only one of the reviews carried out by advanced spam filtering solutions. More advanced spam filtering solutions – those with higher spam detection rates – use Bayesian Analysis and Greylisting to identify spam from previously unknown hackers.

If advanced filtering solutions identify outbound emails from your group as spam, your IP reputation will suffer until it reaches a point where the IP address is added to the Realtime Blackhole List. As mentioned before, it only takes a misspelled title or the overuse of spam-related keywords or characters for your IP address to be blacklisted.

Bayesian Analysis is one of the tools used in an outbound mail filter to ensure your group’s emails are free of spam. Most advanced spam filtering solutions will also use antivirus software when scanning outbound emails to ensure they do not include malware or links to malicious websites.