News: New software version



The latest version of PureMessage Unix, version 6.4, is coming soon. This update will add Sophos Delay Queue to the range of included email security features, helping to stamp out Snowshoe spam – the attackers preferred method of sending spam.

Sophos Delay Queue gives you future proof protection against snowshoe spam - intelligently delaying suspicious mail to run further anti-spam checks. Then automatically rescanning content with updated definitions to increase detection.


Release timelines

The initial release of PureMessage Unix 6.4 is now available via the Sophos Support Team. For customers looking to upgrade their servers to this latest version now, please contact support at

Access to version 6.4 will be available through the regular update mechanism shortly, with an update sent at the time.


How Delay Queue works

  • When the Delay Queue feature is switched on, your email gateway enters an 11-day learning routine to determine your organization’s normal email behavior, recording IP addresses to build a history database and highly-accurate queueing heuristic rules to determine suspicious mail.
  • The gateway then uses these rules to determine how likely a suspicious email is to be spam and moves the email to the Delay Queue. Depending on a how suspicious emails are, they will be held for between 5-60 minutes.
  • As a snowshoe spam campaign is typically over within minutes, during the time the mail spends in Delay Queue SophosLabs will have developed the definitions required to detect any campaign emails. When the mail is released from the Delay Queue, it is rescanned and spam will be blocked.
  • If it still looks suspicious the cycle can be repeated.



  • The update will require you to perform a server update and will not be automatically applied by Sophos
  • Activation of the Delay Queue feature is opt-in. The feature can be activated in your PureMessage Unix admin console once your update to version 6.4 is complete