- When email stops, work stops. Customers wait for answers, suppliers wait for approvals and contracts wait to be signed, usually at the worst possible time.
- Downtime costs Global 2000 companies $15,000 a minute, according to Oxford Economics and Splunk, and email is how most businesses reach customers and suppliers.
- The November 12 Microsoft 365 outage, the fourth widely reported of 2026, disrupted Exchange Online and Teams for more than 10 hours.
- Organizations that route mail through Mimecast can switch to Email Continuity and keep sending and receiving email while the primary platform recovers, so work keeps flowing.
Blog
Microsoft 365 went down. Your customers still expected a reply.
Contracts unsigned, customers waiting, suppliers stuck. The real cost of an email outage lands when you can least afford it.
Key Points
A customer is waiting for an answer. A supplier needs approval. A patient is waiting on a prescription. A contract is ready to be signed.
And your email isn’t working. Outlook was spinning and Teams wouldn’t load. Email is still how the formal side of business runs: contracts, notifications and confirmations.
Your customers don’t see the Microsoft service health dashboard. They don’t know whether Exchange Online has a configuration problem or an infrastructure failure. They just know they haven’t heard back from you.
This isn’t about having a plan on paper. It’s about the real cost at the worst possible moment, when the company stops moving forward.
That’s the reality of an email outage. On November 12, organizations around the world lived it, including ours. Our teams felt it, but Mimecast’s services didn’t stop.
What happened on November 12?
Microsoft experienced a widespread disruption affecting Exchange Online, with issues also reported across Teams, SharePoint, Copilot and Defender.
Users reported problems accessing mailboxes and sending or receiving email. Microsoft investigated infrastructure failures that left servers unable to process requests. Recovery continued into November 13.
Cyberattacks and outages end the same way: no email. Whether the cause is a cloud failure or an attack, organizations that rely on a single provider have no fallback. That is why continuity matters as much as protection, whether the primary platform is down or under investigation.
If Microsoft 365 goes down, does your email go down with it? And do you operational services go down with it?
The problem with technology that almost never fails
Microsoft 365 is a highly reliable platform.
That’s precisely why availability is so easy to take for granted. When something works almost every day, planning for the day it doesn’t (disaster recovery and business continuity) slips down the priority list. Then, one Thursday, the outage happens.
We invest in protecting email against phishing, malware, account compromise and data loss, but people also need to use email when their primary provider is unstable. Customers, suppliers, partners and regulators don’t stop communicating just because your technology has.
Related Tags
- Email & Collaboration Security
