I have been using Zoho mail for about a year and half now for our business.  I have been sending invoices in QB for longer (previously with our gsuite account).  Suddenly today, I am getting the message below.  I believe it is a QB issue but not sure.  I'm also not sure if it has something to do with the authentication stuff.  Can anyone tell me how to tell zoho to tell QB it's ok to send the invoice?  It's super frustrating because my clients pay us online and can't now. QB is not being of any help whatsoever (they want more money to be more helpful).

I've attached a screen shot of the error.  

Thank you