// 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 60
DNS 52
SPF 40
Reputation 39
DMARC 38
DKIM 34
Security 26
Gmail 21
Blacklist 18
Microsoft 365 17
Mailing list 16
Content 15
Mail server 13
Headers 12
Reverse DNS 12
SMTP 12
Spam score 12
Outlook 10
MX 9
Amazon SES 7
Google Workspace 5
TLS 5
Yahoo 5
Mailgun 4
Postmark 3
Apple 2
SendGrid 2
WordPress 2
Zoho 2
ARC 1
BIMI 1
Cloudflare 1
E-commerce 1
GMX 1
Resend 1
T-Online 1
3 guides · tag Postmark
| Problem | In short | Tags | |
|---|---|---|---|
| Postmark error 406 "Inactive recipient": how to fix it | Postmark returns ErrorCode 406 when a recipient hard bounced, complained or was suppressed. See how to find why and when it is safe to reactivate. | Fix it | |
| Postmark 400 "From address is not a Sender Signature": fix it | Postmark returns ErrorCode 400 when your From address is not a confirmed Sender Signature or verified domain. Here is how to fix it for good. | Fix it | |
| Postmark custom Return-Path (pm-bounces) and DMARC alignment | Set up a custom Return-Path in Postmark so SPF aligns with your domain for DMARC. CNAME pm-bounces to pm.mtasv.net, verification and common mistakes. | Fix it |
Not sure what is wrong?
Send a test email or scan your domain: the report tells you which problem you have.