Microsoft Bulk Complaint Level (BCL) & Spam Confidence Level (SCL) deliverability

Question

recently we have a huge drop in response and delivery and after running a inbox placement test from different providers we have discovered that our emails never arrive to inbox and end up in the junk folder

this is caused by

Microsoft Bulk Complaint Level (BCL) & Spam Confidence Level (SCL)

we are using Sparkpost , Mailgun and Elasticsemail with different domains and get almost same delivery results , junk folders. and support is not really helpful.

All our domains are DKIM , SPF and DMARK valid almost 0 complain rate and below 3% bounce rate

we add one-click unsubscribe and check content for spam words. All subscribers are double opt in As well as run bounce validation every 2-3 month

when checking the email inside the Microsoft office 365 we have discovered following headers

X-Ms-Exchange-Organization-Scl 5 X-Microsoft-Antispam BCL 7

we are a bit frustrated and not able to understand what is causing spam filter triggering how to understand why all of our domains get the same score

Answer 1

Hi, @Dmitri Oleinikov

Based on your description, I understand that you have done many things right. However, BCL and SCL are affected by a variety of factors. Things like user engagement, email engagement, data volume surges, irregular sending patterns, low email engagement rates (low open rates, low click-through rates), and more can negatively impact your sender reputation.

Some time ago, EOP made improvements to bulk detection and BCL from 6 to 7, which is more accurate for spam detection, which may be the reason for a significant drop in your email response and delivery.

To improve the situation, you can try the following suggestions:

1.Administrators can use bulk senders insight tool and adjust their BCL settings to optimize bulk filtering and manage false positives and false negatives. During and after the rollout, admins should monitor email flows to assess the impact of these changes on their bulk email management. If any false positives occur, administrators should test and experiment with higher BCL levels to ensure that the updated thresholds effectively meet their organization's screening requirements.

More information can be found:

Bulk senders insight - Microsoft Defender for Office 365 | Microsoft Learn

Bulk complaint level values - Microsoft Defender for Office 365 | Microsoft Learn

2.Optimize your anti-spam strategy to meet your organization's needs.

3.Certain content features may trigger filters, which are not just "spam words", avoid excessive use of images, links, and ensure a good text-to-image ratio.

4.Make sure your email list is clean and up-to-date. Communication with suspicious users can also degrade your sender's reputation.

5.Encourage recipients to add your email address to a whitelist or contact.

It is important to note that it can take a long time to improve your email deliverability and you may need to adjust your practices over time.

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