8 Ways to Help Avoid Postini Filtering

Did you hear it too?  It was the cheers of joy across the email industry earlier this year when people thought Postini was going away and their filtering issues would be over.  As we soon realized, Postini filtering isn’t completely going away, but it is transitioning into Google Apps beginning in 2013.  While some features will be phased out, updated filtering and security features will exist under a new name within Google Apps.  Until then, Postini will continue as a stand-alone product for many users until they either choose to transition to Google Apps over the next year or terminate their contract.  Google expects the transition to be complete by 2014. 

Once everything is said and done, don’t anticipate Google becoming any more forthcoming regarding how to get into the inbox.  The existence of spammers and phishers requires ambiguity around their filtering practices and this will likely continue.  Back in May I discussed the various types of content filters you may encounter when deploying your email program.  While the various filters can create challenges as you try to reach the inbox, it’s no surprise the one that clients tend to ask about the most Postini.  According to the latest Return Path Email Intelligence Report, Postini continues to be the most challenging and widely used spam filter delivering only 23% of email to the inbox while Google Apps allowed 91% of email into the inbox.


Since I just heard the deep sighs of frustration, let me offer a few glimmers of hope.  My colleague Jeremy McGuire, Product Manager, has been conducting some research and testing that helped us uncover the following 8 tips that may help you cheer again when it comes to passing Postini filtering over the next year as well as into the future with Google Apps:

  1.  Your subscriber has a lot of control.  Per the Google Apps transition FAQs, Gmail spam filtering “responds to input from the user about what is spam or not.” What this means is that your subscribers will “train” the filter based on marking or unmarking your messages as spam.  Low complaints and high “this is not spam” rates send a positive message that your subscribers want your mail in their inbox.  Ensure you follow opt-in subscription practices that sets clear expectations regarding the type and frequency of the email subscribers will receive from you.  Follow through by only sending targeted, relevant email to keep subscribers happy and engaged with your program and away from the spam button. 
  2. Authenticate your mail.  Avoid looking like you could be spoofing mail by telling the industry you are who you say you are by properly authenticating your mail with SPF, DKIM and DMARC. For more resources on authentication, visit our Email Brand Monitor page
  3. Avoid Base64 Encoding.  The use of Base64 encoding is a tactic commonly used by spammers to hide the html in an effort to avoid content filters.  If Base64 Encoding is used, your message will likely end up in the bulk folder.  Instead, ensure you build your messages using compliant and clean HTML.
  4. Ensure your links aren’t blacklisted or inactive.  Check to see if any of your URLs are on URL/domain based blacklists like URIBL and SURBL.  If listed, work to get removed from the blacklist or change the link in your content.  On a similar note, ensure all URLs within your content are active and resolve to the proper place.  The presence of blacklisted and/or inactive URLs in your content will negatively affect your reputation with Postini and your inbox placement. This includes 3rd party URLs, too, like bit.ly and other URL shortners, and even advertisers.
  5. Be careful when creating your subject line.  Various key works and symbols in your subject line can trigger the Postini filter.  Avoid the use of the prefix “ADV:” (for advertisement), dollar signs or multiple exclamation points.
  6. Avoid using anything that resembles a credit card or social security number in your content.  Postini has a filtering feature that looks to match number patterns and/or sequences that look like you could be referencing or trying to collect a credit card or social security number.  This is a red flag that you are a potential phishing message and will result in the message getting blocked.  The following are examples of the patterns that will trigger the filter: 

16 digit number patterns (credit card):

  • n nnnn nnnn nnnn nnnn
  • nnn-nnnn-nnnn-nnnn
  • nnnn nnnn-nnnn nnnn
  • nnnnnnnnnnnnnnnn

9 digit number sequences (social security) – these digits can be separated by spaces dashed or periods:   

  • nnn-nn-nnnn
  • nnn nn nnnn
  • nnn.nn.nnnn
  • nnn-nn nnnn
  1. Watch for Spam Assassin and other filters to give you clues.  The various filtering companies that exist all have the same goal – to block spam and only let the legitimate mail through.  Our testing revealed that when various Spam Assassin rules were flagged as a problem, the message was also negatively impacted at Postini.  Since Postini is not very forthcoming regarding why your message is being filtered, take note of what other filters like Spam Assassin do reveal to you and make the appropriate adjustments.
  2. Test!  Test message content to isolate what is causing the filtering issues, such as subject lines, URLs/links, text and images.  Content testing can be a time consuming process as you’ll want to test the various message components separately until you identify what is passing and failing the filter.

This, by far, is not an exhaustive look at why Postini filters email. I’m sure you’ve run across your reasons, and tactics to get delivered to the inbox. Share your experiences in the comments!

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