Unable to send email via smtp

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1

I have the same smtp information registered for all development, staging, and production, but I get errors sending emails outside of the development environment.

I would appreciate it if someone could tell me what the cause is.

Log of sending error]
{
“date”: “2025-06-26T12:16:24.739Z”,
“type”: “fn”,
“description”: “To: {address}”,
“connection_id”: “”,
“ip”: “221.103.226.216”,
" details":. {
“email_type”: “try_provider_configuration_email”,
“notification_type”:. “try_provider_configuration_email”,
“to”: “{address}”,
“error”:. “Error sending email:. Invalid login: 535 Error: authentication failed, authentication failed, authentication failed, authentication failed, authentication failed 535 Error: authentication failed, system busy”
},
“user_id”:“”, “user_name”. “”,
“user_name”: “{address}”,
“environment_name”: “prod-jp-1”,
“log_id”:. “900202506261216838394000000000000001223372040953481646”,
“tenant_name”: “{tenant}”,
“_id”:. “90020250626121624838394000000000000001223372040953481646”,
“isMobile”: false,
“user_agent”: “false”. “Other 0.0.0 / Other 0.0.0”,
“id”: “90020250626121624838394000000000000001223372040953481646”
}

Translated with DeepL.com (free version)

3

Hi @Koki-1205,

Welcome back to the Auth0 Community!

The error above is an authentication error happening on the Email Provider’s end and is likely caused because the SMTP provider rejects the request due to the fact that the submitted credentials do not have the necessary permissions.

You can check out this knowledge article that provides the steps needed to resolve this issue.

I hope this helps!
Thanks,
Remus

4

Thanks to @remus.ivan
for contacting me.

I checked the article, but I am using a custom smtp provider and it didn’t seem to be helpful.
(I use Lark provided by ByteDance to manage my email).

Also, what I am most curious about is why only smtp in the development environment is working correctly.

I am using the same information in all environments, do you know why it is not working outside of the development environment?