Earlier this week two emails I sent from my Fastmail account to an email address on a particular domain were blocked. They bounced back to me via Fastmail's host, mailout.nyi.internal.
With identifying details redacted, the bounce message reads as follows:
Quote:
This is the mail system at host mailout.nyi.internal.
I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.
For further assistance, please send mail to postmaster.
If you do so, please include this problem report. You can
delete your own text from the attached returned message.
The mail system
<xxxxxxxxx@dddddddd.com.au>: host
au-smtp-inbound-1.mimecast.com[nnn.nn.nnn.nnn] said: 554 Email rejected due
to security policies - https://community.mimecast.com/docs/DOC-1369#554
[gZyIIRMdO8K-GC40uA7CCg.au58] (in reply to end of DATA command)
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Earlier this year emails I sent to another address at the same domain were also blocked and bounced. A similar bounce message was sent to me within minutes.
The individuals to whom I sent these messages are very well known to me and it is exceedingly unlikely that my Fastmail email address is not in their respective email address books. The blocking is happening at the email server for the domain, I think.
I tried to contact the people managing the email server of the domain by forwarding the bounce message to "postmaster@dddddddd.com.au" but this message also bounced.
Following this I sent a similar request for assistance to "postmaster@fastmail.com". This message did not bounce but I have not received a reply.
I would appreciate advice on how I might resolve this problem with the management of the email server. Who do you suggest I should contact? Is there a more appropriate email address format that is widely used in the tech industry to contact email service managers? Should I create a support ticket for Fastmail?
The email service at this domain is provided to a large number of disparate subscribers working in the same service industry who by and large are not particularly tech savvy. For many years the people who managed their web and email access provided scant attention to security issues. One result was that some thousands of more or less tech clueless subscribers had their email accounts bombarded with spam, spam with malware payloads, phishing attacks, the works. Stories of cyber attacks on this bunch of subscribers and others in the same industry hit the local news over the last year or so. I think the tech wizards dealing with these subscribers' email are paying much more attention to security concerns nowadays, which is probably why my messages have been getting bounced.
Cheers,
David