The SMTP server: 5.7.0 Authentication Required

I am using the cloud version of Manager.
I have a number of businesses set up within Manager.
All invoices from Manager use the same email google email address: muds.help@gmail.com
I started to receive the error message “The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.7.0 Authentication Required. Learn more at”

I read the help guides and related issues on Manager Forum.
I then went to Google and changed
When I tested the email in Manager for one of the businesses, I got this message: ‘Test message has been successfully sent.’
When I tested the email in Manager for another business. I got this message: "The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.7.0 Authentication Required. Learn more at’

I do not understand how this is possible as both businesses use the same gmail address.

One you are sending in plain text, the other in HTML. Was that a setting on the gmail side of things?

I have changed the passwords on gmail and for some reason I do not understand, that appears to have resolved the issue. I’ll let you know if it happens again.

Thanks for your support.