If you are trying to send emails and get a message like:
then it could be a temporary issue. If the message says:
"No action is required on your part. Delivery attempts will continue for some time, and this warning may be repeated at intervals if the message remains undelivered. Eventually the mail delivery software will give up, and when that happens, the message will be returned to you."
then the receiving email may have problems.
If you experience this error everytime, please contact Boundless Technologies so we can test your email and POP client settings.