Email anti spam software is a service that complements an existing email filter in order to improve its spam detection rates. In most cases, a standard email filter detects around 97% of spam emails, growing a spam detection rate of around 99% when acceptable spam thresholds are amended upwards.
However, in some larger companies, a spam detection rate of 99% is enough to prevent the business continuing to receive a considerable amount of spam. As the 1% of spam emails that avoid detection are likely those with the highest level of sophistication, they are also those with the most dangerous threat level.
Additionally, by raising acceptable spam thresholds too high, genuine emails can be quarantined as spam (false positives), delaying the sending of business-critical communications. An email anti spam service with a high spam detection rate can resolve this problem without causing unreasonable delays.
An email anti spam service has many of the tools often found in existing mail filters. These include RBL and SURBL filters, recipient verification and Bayesian analysis (the tool that rates the level of spam in each email for the purposes of blocking it or permitting it subject to the acceptable spam threshold).
Whereas RBL and SURBL filters are good at spotting emails from known sources of spam, if a spammer uses a different server with a different IP address, the filters are not always the best solution. By comparison, an email anti spam service has a greylisting function to spot emails from previously unknown sources of spam.
The greylisting function operates by declining every inbound email. The email is returned to its originating server with a request for it to be sent again. Normally, the email will be returned within a few minutes unless the originating server is too busy to answer the request. In most instances, hackers’ email servers are too busy sending more spam emails to respond and the spam email is never sent again.
In addition to the greylisting function, an email anti spam service employs antivirus software, the Sender Policy Framework protocol and HELO tests to cut the amount of spam a business receives. By using these tools in conjunction with the tools commonly found in existing mail filters, an email anti spam service can result in a spam detection rate in excess of 99.9% – often with no false positives.
Acceptable spam levels can be difficult to get right. Set the thresholds too low, and the company is inundated with spam. Set the thresholds too high and, as mentioned previously, business-critical emails are quarantined in mistake and have to be manually set by system administrators.
Additional problems occur when one department requires a different acceptable spam threshold from another. Finance departments may hope for a high threshold to protect employees from spoofed email, but this could create concerns from sales departments about the timely delivery of sales leads.
An email anti spam service can get around this issue by allowing administrators to apply different acceptable spam thresholds to different groups of staff, different thresholds can be applied to individual employees if necessary, and the process is made easy by having the facility to integrate spam detecting services with directory tools such as Active Directory and LDAP.
Along with the integration facility, each business’s email anti spam service is managed using a centralized administration portal. Administrators can adjust acceptable threshold levels, whitelist or blacklist senders, and manage web authentication settings with the click of a mouse. Once the optimal settings have been created, an email anti spam service is a set and forget solution to spam emails.
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