SMTP Error: data not accepted

When checking out and confirming the order I get this error message:
SMTP Error: data not accepted.SMTP server error: DATA END command failed

There is nothing wrong with the smtp settings, only from the eshop.
Please help..

Hello Christin,

As the error shown, I am pretty sure that it caused by wrong SMTP settings. Did you try to send the email from your website? Does it work?

Sincerely, Giang

Yes, the joomla system sends both test email and user email when registering.
That's why I don't understand the error message.
Could it have anything to do with time out? Of 7 orders, admin received 1 email notice....
And even though an email was sent, I got the same error message...?

Regards.
Christin

That's sound like a strange issue. Please submit a new ticket to EShop category so I can help you to check if I can see any thing.

Sincerely, Giang