The error message "535 Incorrect authentication data" is typically associated with email authentication issues, and it doesn't specifically relate to email warm-up. This error message indicates that the email server or email client attempting to send an email message is providing incorrect authentication credentials during the SMTP (Simple Mail Transfer Protocol) authentication process.
SMTP authentication is a method used to verify the identity of the sender and ensure that they have permission to send email through the server. It's commonly used to prevent unauthorized access to the email server and to prevent spam.
Here's what this error might mean in the context of email warm-up:
Incorrect Credentials: The email server or client you are using to send emails during the warm-up process is providing the wrong username or password for authentication.
SMTP Configuration: The SMTP server settings, such as the server address, port number, or encryption method, may not be correctly configured in your email client or sending software.
Account Lockout: Multiple failed login attempts may result in temporary account lockout for security reasons. This could prevent you from sending emails until the lockout is lifted.
Email Service Provider (ESP) Issue: If you're using an ESP to send emails, there might be a configuration issue on their end, or they might have changed their authentication requirements.
To resolve this error in the context of email warm-up, you should:
Double-check the username and password you're using for SMTP authentication.
Ensure that your SMTP server settings are correctly configured, including the server address, port number, and encryption method.
Verify if there are any issues or changes with your email service provider's authentication requirements.
Check for any temporary account lockouts and wait for them to be lifted if applicable.
It's important to note that email warm-up primarily involves gradually increasing your email sending volume to establish a positive sender reputation with email service providers. Authentication issues like the one described by this error message can hinder your warm-up process, so resolving them is crucial to ensure successful email delivery during the warm-up period.
