Suddenly getting error of Invalid login: 535 Authentication failed

i, I have been sending emails in Unity for the last 5 days without any issues. The emails were successfully delivered to users, but suddenly I started encountering an error: ‘Failed to send email: 535 Authentication failed’. Could you please assist me with resolving this issue?

Uh… Unity?

If this is a Ghost question, please provide a lot more detail about your hosting and email setup.

If this is a Unity question, I’m not sure why you’re asking it here…