Authentication (SPF, DKIM, DMARC)
35 articles
“Message rejected due to DMARC policy”
The bounce message "550 5.7.26: Message rejected due to DMARC policy" indicates that the recipient’s mail…
Resolving SPF “Softfail” vs. “Hardfail”
If your email headers display Received-SPF: softfail or outbound messages bounce with SPF authentication errors, your…
How to Generate 2048-bit DKIM Key in Admin Console
DKIM (DomainKeys Identified Mail) prevents email spoofing by attaching an asymmetric cryptographic signature to outbound messages.…
Why Email is Marked “Via [Service]” or “On Behalf Of”
When recipients view an email in Gmail, they may notice a secondary domain tag next to…
Fix: “550 5.7.1” Authentication Required
When an SMTP mail client, network scanner, web application, or automated script attempts to send email…
Troubleshooting “Too many lookups” in SPF
When your SPF record triggers a “too many lookups” error, major email providers like Gmail and…
How to Resolve DMARC Policy Rejects: Reject vs. Quarantine
When an external mail server blocks your outbound messages due to a DMARC policy enforcement rule,…
“Unauthenticated Email from [Domain]” Warning
The “Unauthenticated Email from [Domain]” warning appears in Gmail when an incoming message fails baseline domain…
Resolving “Message not authenticated by DKIM”
When Google Workspace logs or recipient bounce-backs flag an outbound email with the status “Message not…
How to Fix Gmail Error 550 5.7.26: SPF Missing/Invalid
When your outbound emails are rejected with a 550 5.7.26 error code, your domain has failed…
Gmail Authentication & DNS Failures: Fixing SPF, DKIM, and DMARC
When outbound emails fail to reach their destination, bounce back with cryptic 550 codes, or trigger…