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535 5.7.8
SMTP Error 535 5.7.8: Authentication credentials invalid
Error✕ Not retryable · fix the payloadNetwork
TL;DR · 10-second read
SMTP AUTH failed. For Gmail/Workspace use an App Password (2FA required); for ESPs use the SMTP-specific credentials, not your dashboard password.
Identify: does your log match?
What you see · exact log / response
535-5.7.8 Username and Password not accepted. For more information, go to 535 5.7.8 https://support.google.com/mail/?p=BadCredentials - gsmtp
Fix
Being written
Copy-paste fixes for 535 5.7.8 are in the enrichment queue
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Last verified 2026-10-16 · Source: RFC 5321 reply codes + RFC 3463 enhanced status codes (IANA registry) · Official docs ↗ · ~8,100 searches/mo