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How Gmail spam and virus filtering differs from Postini

Once your orgs, users, and settings are transitioned from Postini to Google Apps, you'll automatically begin using the Gmail spam and virus protection instead of Postini's. You should expect the Gmail and Postini filters to behave differently, acting more strict or lenient on different types of mail.

Spam filtering differences

One of the basic principles of the Gmail spam filtering system is that it responds to input from users. Gmail users can “train the system” by clicking Report spam or Not spam. The more frequently a user reports spam (or indicates that a message is not spam), the more effective this filtering mechanism becomes.

Note: Gmail does not require explicit interaction by the user to manually adjust thresholds or add approved or blocked senders. However, as users mark messages as spam or not spam, Gmail customizes filtering behavior for those types of messages.

Following their transition to the Google Apps platform, non-Gmail users (for example, users on Microsoft Exchange) can manage spam using Message Center and the quarantine summary. These enable non-Gmail users to mark messages as spam or not spam

Note: Spam messages are stored in the Google Apps platform for 30 days, while Postini typically stores messages for 14 days.

How should admins and users deal with bulk email messages?

Gmail handles promotional emails differently than Postini. Postini tends to filter certain types of marketing-related or special-offer bulk mail, while Gmail is more likely to allow this type of mail through. A simple way to think of it is that mail landing in the Gmail Promotions tab likely would have been blocked as spam by Postini.

By allowing users to train the system by identifying messages as spam or not spam, Gmail provides fine-grained control over which bulk mail your users will receive without the direct use of approved and blocked senders lists. Filtering in Gmail is more dynamic because it's able to learn more quickly and in a more personalized way.

Following your transition to Google Apps, you can can manage undesirable bulk mail in the following ways:

  • Gmail users and users with non-Gmail mailboxes can click the unsubscribe link at the bottom of the email message.
  • Admins can turn on aggressive spam filtering to enforce more stringent filtering of bulk mail.
  • Admins can add the sender to a Blocked sender list.
  • Admins can block the messages using the Content compliance setting.
  • Gmail users can enable the Smart Labels lab (not available for non-Gmail mailboxes).
  • Gmail users can click the Report spam button (not available for non-Gmail mailboxes).
How to file a Support case for systemic spam issues

If you experience spam issues that are affecting your organization systemically, please submit a support case. See the Transition Support page for details.

How can an administrator prevent users from viewing spam?

An administrator can set up an admin quarantine to capture a message prior to delivery and place it into a queue/quarantine that is accessible only to administrators or to another appropriate designee. The admin can then release the message for onward delivery or choose to not do so.

Message Center and quarantine summary

Non-Gmail users are unable to train the Gmail system by clicking the Report spam and Not spam buttons. However, Message Center and the quarantine summary enable this functionality. 

Message Center

Message Center is a web-based console that enables non-Gmail users to manage their spam messages. Message Center is available for organizations that use a non-Gmail mail service such as Microsoft Exchange (or other non-Google SMTP service). In Message Center, users can identify a message as not spam and deliver it to their non-Gmail inbox.

Message Center enables users to add approved senders at a user level. Message Center doesn't include an editable per-user blacklist, but when users mark messages as spam with Message Center, this is equivalent to adding the sender to a blacklist.

One of the advantages of Message Center is that it enables non-Gmail users to find and report “false positive” emails—emails that are falsely categorized as spam and not delivered to the user. For more information about Message Center, see Set options for non-Gmail mailbox users. For user instructions, see Manage messages in Message Center

Quarantine summary

If your organization uses a non-Gmail email service such as Microsoft Exchange, you can use the Non-Gmail mailbox setting in the Google Admin console to reroute messages to your users' non-Gmail mailboxes, and to set up a quarantine summary for your non-Gmail users.

The quarantine summary is comparable to what users experience with Postini. It’s a digest that lists all messages that were marked as spam. It's delivered to users in their inbox and enables them to identify a message as not spam and deliver it to their on-premise inbox. (Non-Gmail users who transition to Google Apps can't do this without the quarantine summary.)

During your service migration, your Postini quarantine summary settings are moved to the Non-Gmail mailbox setting. For more information about quarantine summary reports, see Set options for non-Gmail mailbox users. For user instructions, see Quarantine summary report.

Virus filtering differences

Gmail has comprehensive virus protection that includes the following benefits:

  • Rejection of messages with executables—Gmail automatically rejects messages that have executable file attachments, even if those files are compressed into another file, such as a zip or rar file. We do this for many types of executable files (see Some file types are blocked). Gmail also automatically rejects messages that contain a password protected zip file within another zip file.
  • Automatic scanning of attachments—Gmail automatically scans every attachment when it's received, and automatically rejects messages that contain viruses.
  • Increased protection against phishing—Gmail provides increased protection against phishing-based attacks and messages containing URLs that point to malicious sites.
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