The SMTP login failed: the username or password was rejected.
Policy rejection · fixable
Common causes
- Wrong password or username
- The provider requires an app password (Google, Microsoft with MFA)
- SMTP AUTH disabled for the mailbox (common in Microsoft 365)
- Account locked after too many attempts
How to fix it
- Re-enter the full email address as username and the correct password
- Create an app password if two-factor authentication is on
- In Microsoft 365, check that Authenticated SMTP is allowed for the mailbox — Microsoft is retiring basic authentication for SMTP AUTH, so you may need OAuth or a relay service
SMTP TesterRun the right check for your domain or paste the full bounce message for a precise explanation.
Open SMTP Tester →Frequently asked questions
Why does Gmail reject my correct password for SMTP?
With 2-Step Verification you need an app password for SMTP; the normal account password is not accepted.