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5 Things About Outlook Junk Email Filters a Business Should Know

By August 7, 2015October 21st, 2021Blog

Microsoft Outlook had an estimated user base of between 500 and 600 million in 2014, making it one of the the world’s most popular email clients and a tool that a huge number of businesses rely on. Despite its ubiquity, Outlook has some notable problems, especially in terms of email filtering.

Effectively diverting unwanted messages and ensuring that important emails are not incorrectly flagged is imperative for all businesses, many of which rely on Outlook junk email filters exclusively. With that fact in mind, we’ve put together a list of five things you should know:

1. The Filters Scan Every Incoming Message

Until just recently, Outlook relied on a “Messaging Application Programming Interface” to screen incoming emails for spam. Now all messages pass through an email filter regardless of what kind of preferences the user has set. That means problems inherent in the filters or hacks devised by email scammers affect every message sent towards your inbox. By relying on a single line of defense, the entire inbox is left vulnerable.

2. The Filters Do Not Learn on Their Own

Unlike more advanced measures, Outlook junk email filters do not evolve as they learn more about the current nature of spam and the user’s preference. They can be pushed in this direction, but only if the user takes the time to mark unwanted messages as spam. In practice, this takes as much time as deleting the emails and produces uncertain results. Even then, Outlook is notorious for marking legitimate messages as junk. Don’t count on Outlook filters to improve on their own.

3. The Filters Do Not Automatically Disable

You may have heard about the problems with Outlook junk email filters and already sought out an alternative. Be aware that unless you have specifically disabled them, the filters are still evaluating every message that hits your inbox. Even if you have upgraded to a better solution, important messages might still get routed to your junk folder.

4. The Filters Have Limits

Users can take steps to refine filters by creating lists of senders and domains that are safe and lists that are blocked. Unfortunately, these lists are limited to a total of 510 KB of data overall. That might sound like a lot, but many businesses have vast lists of safe senders and even larger lists of blocked senders. Users who are proactive about fine-tuning their Outlook spam email filters could quickly reach their limit and face inbox chaos in the future.

5. The Filters Only Separate Spam

Best practices dictate that users periodically review their junk email folder for legitimate messages that have been incorrectly diverted. Considering how often this is an issue, frequent checks are usually necessary. The issue is that when there is uncertainty about the efficacy of the filters, users are enticed to open all junk messages that appear legitimate. These could be carefully disguised phishing scams and expose the user to malware and other threats. Since the Outlook filters can’t be reliably trusted, they actually make the job of email scammers easier.


If you are ready to upgrade your email security capabilities and disable Outlook junk email filters for good, learn more about Sendio’s Op-Inbox.