I'm getting this error and am not able to send any mail today (for hours) - which is a big problem for my customers.

"Unable to connect SMTP server:smtpout.mail.zoho.com Reason:Authentication failed:554 5.1.8 Sender Address Blocked"

After looking into the forums, it also was unclear if it was because of attachments or an excess of emails.

Can you please unblock my email?

Thanks