Applications » What is Office 365 spam filter

The spam filter on Office 365 comes in for quite a bit of criticism. Although Microsoft regularly introduces new features to improve its spam detection rates, many of these are paid-for features or only available as part of an Exchange Online Protection subscription. Others (for example “IP throttling”) cause users more distress than the spam emails the feature is meant to prevent.

One of the reasons why the Office 365 spam filter fails to detect spam is that Microsoft spam filters work retrospectively. Only after a customer has reported a spam email will Microsoft add the IP address to its “real-time block lists” and include the blacklisted IP address in the next software update. With spammers frequently changing IP address, retrospective updating is generally ineffective.

IP throttling was supposed to resolve this issue by blocking emails or giving a low Spam Confidence score to emails originating from sources with no “IP reputation”. This resulted in emails from legitimate businesses new IP addresses being flagged as spam; and, when Microsoft launched a self-service IP Delist Portal to help businesses with new IP addresses get around their lack of IP reputation, it gave spammers the opportunity to delist their blocked IP addresses – exacerbating the problem.

I hope this information helps!
Regards,
Lewis
Tech-consultant
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