Net::SMTPAuthenticationError: 435 4.7.8 authentication failed

Server just randomly crashing with with this error.

An error occurred when sending a notification using 'email' notifier. Net::SMTPAuthenticationError: 435 4.7.8 Error: authentication failed: UGFzc3dvcmQ6

What is that supposed to mean? This is a project written by not me, so I am a little confused.

As I know, UGFzc3dvcmQ6 means "password". To I need to configure ActionMailer password then?