A DKIM-Signature found in the message has duplicate tags. Mail servers will reject this DKIM-Signature and mark it as a fail as duplicate tags are forbidden.

MxToolbox Delivery Center

This is one problem. Inbox providers check every layer.

Gmail, Yahoo! and Outlook check your email at several layers before it reaches the inbox. Delivery Center monitors and manages every one of them, so you find and fix problems before they cost you delivery.

DMARC, SPF & DKIM
Blacklists
Inbox Placement
Spam complaints
Impersonation protection
BIMI
Mailflow

Email MarketersTest inbox placement and stay inside bulk sender spam-rate limits.
DMARC AdoptersSee every sender and know when it's safe to enforce.
IT Email AdministratorsCatch DNS, authentication and mailflow changes with alerts.

See Delivery Center

$129/mo · 30-day money-back guarantee · Compare all plans