MailGenius Responds After Outlook Algorithm Hits Email Deliverability Hard

MailGenius, the leading email deliverability testing platform, alerts marketers and business owners to Microsoft Outlook’s newly enforced email algorithm update, which took effect on May 5, 2025. This marks the fourth major update across top inbox providers in just two years, joining Gmail, Yahoo, and an earlier Microsoft rollout. It’s fueling a dramatic increase in spam filtering and email blocking.

Troy Ericson, CEO of MailGenius, commented, “Open rates are down. Click rates are down. Sales are down — for most companies sending marketing emails. Not because the content is bad, but because aggressive new algorithms are decimating deliverability. Outlook is now filtering emails more strictly than ever before, and we’re seeing a sharp rise in delivery failures across accounts that haven’t adapted.”

The 2025 Outlook Update: What’s Changed?

As detailed in Microsoft’s announcement, the update focuses on tightening authentication enforcement and spam prevention through:

• Mandatory domain alignment between SPF, DKIM, and DMARC
• Heightened spam sensitivity toward promotional copy, misleading links, and inconsistent sending patterns
• More aggressive throttling and blocking for unauthenticated bulk senders
• Increased filtering of graymail and transactional messages without domain reputation history

Many marketers are now discovering that even well-designed, personalized emails are getting flagged, especially when sent through shared IPs or misconfigured DNS records.

A Pattern Marketers Can’t Ignore

“Between Gmail’s update last year, Yahoo’s rollout in Q1, and now Outlook’s overhaul, inbox algorithms are rewriting the rules of email marketing,” Ericson said. “We’ve seen more marketers frustrated in the last six months than in the last six years combined. If your domain isn’t properly authenticated or your list hygiene isn’t airtight, your emails might not even get delivered, let alone opened.”

The consequences are severe: companies are losing out on high-value engagement, automated workflows are breaking down, and ROI on email marketing is plummeting.

“The solution? Using email testing tools first, then sending,” added Ericson. “Here at MailGenius, we offer a free Email Deliverability Audit for anyone impacted by the Outlook changes.” This audit includes:

• A full SPF, DKIM, and DMARC authentication check
• Real-time spam filter diagnostics and email inbox placement testing
• Blacklist scanning and domain health reporting
• One-on-one consultation with MailGenius deliverability experts

“We’ve already helped companies recover 10 percentage points or more on open rates by simply fixing what Outlook’s filters flag as risky — and now we’re helping companies get back into the inbox altogether after they had been blocked entirely by the most recent update,” Ericson shared. “This isn’t a guess-and-check game anymore. You need precision diagnostics and expert intervention.”

In response to the widespread impact of Microsoft’s algorithm update, MailGenius urges all high-volume email senders, especially those using Outlook for B2B or transactional messaging, to schedule a free audit immediately.

If declining performance, rising bounces, or confusing delivery metrics are popping up, run a full email health check before running another email campaign. Visit www.MailGenius.com for a free deliverability audit today to protect inbox reach before it’s too late.

About MailGenius

MailGenius provides email deliverability services to test and help businesses understand and navigate the complex world of email deliverability. Their goal is to ensure that every email lands in the primary inbox, not the spam folder.