Outlook Deliverability: A Silent Shift with Serious Consequences

Starting on June 17th, 2025 at 11:10 UTC, multiple high-volume senders – particularly in France – began experiencing a sudden surge in DKIM failures on emails sent to Microsoft domains (Outlook, Hotmail, etc.). These bounces occurred even though SPF and DMARC were properly configured. What We’ve Observed Our engineers quickly identified the root cause: a […]

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Categories: Authentication, Deliverability, Providers

Explore Postmastery’s New YouTube Channel Featuring Highlights from the Postmastery Day 2024 & EMAS.

We are pretty excited to announce the launch of Postmastery’s brand new YouTube channel, what we hope will be a hub for insightful and engaging content on email deliverability. Our first uploads feature sessions from the very first Postmastery Day at the Deliverability Summit, held at The Rosarium in Amsterdam on April 11, 2024. This […]

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Categories: Authentication, General, General

All the bounce we cannot see: A Deferral story

When we work in email deliverability, we constantly hear about the processing of bounces, sometimes about blocking bounces and more often about suppressing bounces… In short, as you will have understood, processing bounces is the absolute prerequisite to email deliverability … But then, what about Deferrals… Should we process them? And if yes, how? What […]

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Categories: Authentication, Deliverability, Deliverability

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