Issue with SMTP mail transmission failure in Qlik SMTP Connectors.

[qwebnm]

When using Qlik SMTP Connectors and attempting to save inputs and run a table, the following error occurs:
"Error connecting to SMTP server (Authentication failed (535))."

What could be the reason for this error?

The port 10025, which is used for SMTP on the SMTP server, is open.

Why is this happening?

I would appreciate insights from experienced Qlik professionals.

If there are any suspected issues, please let me know.

Thank you.