Gmail 534 5.7.90
App password required
Gmail 534 5.7.90 means: app password required. It is a permanent failure, so do not retry it unchanged. The account has 2-Step Verification, so the client must use an app password or OAuth instead of the normal password.
Gmail’s exact wording
Quoted from Google Workspace Admin Help: Gmail SMTP errors and codes, checked 2026-11-05. Placeholders are Gmail’s own.
Reply text
Application-specific password required. For more information, go to Sign in with app passwords.
Reply text
Please log in with your web browser and then try again. For more information, go to Can't sign in to your Google Account.
| Who sends it | Gmail and Google Workspace |
|---|---|
| Basic code | 534: Authentication mechanism is too weak (RFC) |
| Enhanced code | 5.7.90: Gmail-specific, not in the IANA registry. Its subject digit puts it under 5.7.0 other or undefined security status. |
| Permanent or temporary | Permanent (5xx) |
| Verifying the list prevents it | No |
In practice
Gmail returns this when an account with 2-Step Verification is used from an SMTP client with its normal password. Create an app password in the Google account's security settings, or switch the client to OAuth. The other version asks the user to log in with a web browser first. App passwords are only available when 2-Step Verification is on, and some Workspace domains disable them. OAuth avoids the need for a separate password and is the method Google recommends for apps.
What the sender should do
The account has 2-Step Verification, so the client must use an app password or OAuth instead of the normal password.
Would verifying the list have prevented Gmail 534 5.7.90?
No
This reply is about your sending setup, the message or the receiving system, not about whether the address exists, so verifying the list will not prevent it.
Common questions
- What does Gmail 534 5.7.90 mean?
- Gmail 534 5.7.90 means: app password required. It is a permanent failure, so do not retry it unchanged. The account has 2-Step Verification, so the client must use an app password or OAuth instead of the normal password.
- Should I retry after Gmail 534 5.7.90?
- No. It is a permanent (5xx) failure, so the same message to the same address will fail again. Fix the cause first. The account has 2-Step Verification, so the client must use an app password or OAuth instead of the normal password.
- Would verifying my list have prevented Gmail 534 5.7.90?
- No. This reply is about your sending setup, the message or the receiving system, not about whether the address exists, so verifying the list will not prevent it.
Sources
- Google Workspace Admin Help: Gmail SMTP errors and codes (checked 2026-11-05)
- RFC 4954: SMTP Service Extension for Authentication (checked 2026-11-05)
Registry and provider wording is quoted exactly; guidance is written by the SimpleVerifier Team.
SimpleVerifier Team · Last checked against the sources 2026-11-05