// how to fix
Not sure what is wrong?How to fix email problems
Your test or scan found a problem? Find the matching guide below: what it means, why it matters, and how to fix it step by step.
Bounce 40
DNS 36
DMARC 33
Reputation 33
SPF 30
DKIM 27
Gmail 19
Security 19
Blacklist 18
Content 14
Headers 11
Mailing list 11
Spam score 11
Reverse DNS 10
Microsoft 365 8
Outlook 8
Mail server 7
MX 5
Yahoo 4
TLS 3
Apple 2
Google Workspace 2
BIMI 1
E-commerce 1
GMX 1
WordPress 1
Zoho 1
8 guides · tag Outlook
| Problem | In short | Tags | |
|---|---|---|---|
| Your emails land in Outlook or Hotmail junk | Outlook.com, Hotmail and Live send many new senders to Junk. Check your setup, then use Microsoft's free sender tools: SNDS, JMRP and the delist portal. | Fix it | |
| Gmail shows "via" or "sent on behalf of" next to your name | Recipients see "via another-domain.com" or "on behalf of" because your email is signed or sent with another domain. Sign it with your own domain. | Fix it | |
| Outlook shows "?" or "We can't verify the sender" | Outlook replaces your photo with a question mark or says it cannot verify who sent the email. It means authentication failed; here is how to fix it. | Fix it | |
| Microsoft "451 4.7.500 Server busy": temporary deferral | Outlook.com and Hotmail are holding back emails from your IP because they do not know it or trust it yet. Keep volumes low and build reputation. | Fix it | |
| Outlook.com "550 5.7.1 ... part of their network is on our block list (S3150)": how to fix S3150 and S3140 | Outlook.com and Hotmail refuse your email because your IP or its network range is on their block list (S3150, S3140). Learn how to request delisting. | Fix it | |
| Microsoft 365 "550 5.7.606 Access denied, banned sending IP": how to delist your IP | Microsoft 365 rejects your email because your IP is on its banned list (5.7.606 to 5.7.649). Learn how to use the delist portal sender.office.com. | Fix it | |
| Microsoft "550 5.7.509 ... does not pass DMARC verification and has a DMARC policy of reject": how to fix it | Outlook and Microsoft 365 reject your email because it fails DMARC and your domain uses p=reject. Fix SPF or DKIM alignment to get delivered. | Fix it | |
| Outlook.com "550 5.7.515 Access denied, sending domain doesn't meet the required authentication level": how to fix it | Outlook.com, Hotmail and Live now require SPF, DKIM and DMARC from high-volume senders. Here is how to fix error 550 5.7.515. | Fix it |
Not sure what is wrong?
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