Why Am I Getting the Gmail SMTP Authentication Error '5.5.1 Authentication Required'?

Solving Gmail SMTP identity verification errors: "5.5.1 identity verification required"

When sending an email, the error "SMTP server requires a safe connection or the client is not authenticated by identity. The server response is: 5.5.1 identity verification required" may have a variety of factors.

Reason 1: Password error

Make sure the password provided by the sending address is correct.

Reason 2: Log in from a third -party application

If you log in from applications other than standard Gmail, you may encounter this error.

Solution: Enable the application with low security

Visit https://www.php.cn/link/0A8A64171A9145F6A47E5B3544632E3B .

Enable application options that allow lower security.
1. Reason 3: Geographical restrictions
If you try to log in from the time zone or computer you usually use, Google may mark it as a suspicious event.

Solution 1: Log in from the production server

If you have the right to access the production server, build a remote desktop connection and log in from the browser of the server. This will create an exception and allow login from code.

Solution 2: Enable access from abnormal positions

If you have no right to access the production server, visit

https://www.php.cn/link/22CD4D66FC24FC0163AC00D27C1433C5

and grant the permissions logged in from other positions.

Solution 3: Create a password specific to the application

Enable the two -factor authentication and generate a password specific to the application (

https://www.php.cn/link/5165bb7092845d88fd8FD52D1F32B5 SMTP.

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