Microsoft 365 · Troubleshooting
Why Is Business Email Not Working?
Business email usually stops working for one of four reasons: an outage at your email provider, a problem with one person's account or Outlook, a full mailbox, or settings that send your messages to spam or block them. Start by checking whether it is everyone or one person and whether the problem is sending, receiving, or both. And watch for one warning sign: email rules or forwarding nobody set up can mean the account was hacked.
By SupportMax · Updated October 13, 2026
Check first
1
Is it everyone or one person?
2
Is it sending, receiving, or both?
3
Does webmail work when Outlook doesn't?
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Common causes
Why business email stops working
These causes explain most business email problems.
01
Provider outage
Microsoft 365 or your email host is having problems, so everyone is affected.
02
Outlook or account problems
A stuck Outlook profile, an expired password, or a sign-in problem for one person.
03
Full mailbox
A mailbox at its limit stops receiving new messages.
04
Spam and authentication
Missing or wrong email records make your messages land in spam or get rejected.
Step by step
How to troubleshoot business email
Work through these in order.
Let's Take This Off Your Plate1. Check for an outage
If everyone is affected, check your provider's service status. In Microsoft 365, an admin can see service health in the admin center.
2. Try webmail
If email works in the browser but not in Outlook, the problem is Outlook or the computer, not the mailbox.
3. Look at the error
A bounce message usually says why mail was rejected, such as a full mailbox or a failed authentication check.
What to do
Can't send, can't receive, or going to spam
Match the fix to the symptom.
Can't send
Messages stuck or rejected
Check the bounce message
Confirm the password still works
Check for sending limits
Restart Outlook or try webmail
Can't receive
Nothing arriving
Check mailbox storage
Check junk and quarantine
Look for rules moving mail
Check for a provider outage
Going to spam
Your mail isn't trusted
Check your email authentication records
Avoid sending from personal accounts
Review bulk email practices
Check if your domain is blocklisted
Microsoft explains how to check Microsoft 365 service health, lists fixes for recent Outlook issues, and describes email authentication that keeps your messages out of spam.
Security check
When email problems mean a hacked account
Be suspicious if replies are disappearing, contacts say they got strange emails from you, or you find rules or forwarding nobody set up. Attackers often hide inside a mailbox this way. Change the password, check sign-in activity, remove unknown rules, and see what to do if your business email was hacked.
Microsoft 365 management →How SupportMax helps
How SupportMax handles business email problems
01
Help desk
Your team contacts our help desk when email stops working.
02
Fix
We fix mailbox, Outlook, and account problems in Microsoft 365.
03
Protect
We filter phishing and spam and set up email security settings.
04
Respond
If an account was taken over, we help contain it and recover.
Working with SupportMax
One accountable team, clear next steps
Email problems again?
Let us take it off your plate. Call 310.331.8119, Monday–Friday, 9:00 a.m.–6:00 p.m. Pacific, or start with a free Technology Clarity Assessment.
Questions
Business email not working: common questions
Have a question that isn't here? Call 310.331.8119 or schedule a free consultation.
How do I know if Microsoft 365 is down?
An admin can check service health in the Microsoft 365 admin center. If everyone is affected at once, an outage is likely.
Why do our emails go to spam?
Often because email authentication records are missing or wrong, or because of how bulk emails are sent. Fixing the records usually helps.
Why does email work on my phone but not in Outlook?
That points to Outlook or the computer, not the mailbox. Restarting Outlook or repairing the profile often fixes it.
What if someone's mailbox is full?
Archive or delete old mail, or adjust their storage. A full mailbox stops receiving new email.
Could our email have been hacked?
Unexpected rules, forwarding, or strange sent messages are warning signs. Change the password and check sign-ins right away.
Can SupportMax manage our email?
Yes. We manage Microsoft 365 email, mailboxes, and security, and our help desk supports your team, with 24/7 coverage available as an add-on. See Microsoft 365 management.
Get your email working, and keep it secure
Call 310.331.8119, Monday–Friday, 9:00 a.m.–6:00 p.m. Pacific, or request a free Technology Clarity Assessment. See also email security.
Prefer to call? 310.331.8119 · Mon–Fri, 9–6