I couldn’t find an email address to contact on the website, so I’m posting here.
When trying to send email to server-owner-help@ntppool.org the mail server rejects it with:
This is an automated message from the mail system at Fastmail.
I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. No further attempts
will be made to deliver this message to those recipients.
For further assistance, please read our help center article
about message bounces
https://www.fastmail.help/hc/en-us/articles/7010500320655-Why-messages-bounce-back
If you would like to reach out to our support team about the
issue then please include this problem report.
The Fastmail support team.
redirect.phl-imap-02
<server-owner-help@rt.ntppool.org>: host
mailredirect.phl.internal[/var/run/lmtpforward/redirect] said: 550 5.1.1
<server-owner-help@rt.ntppool.org>: Recipient address rejected: User
unknown in virtual mailbox table via phl-compute-01 (in reply to end of
DATA command)
It looks to be a misconfiguration. I thought I would post here in the hope that one of the administrators of ntppool.org would see it.