Email bouncing

[#1]

For past two weeks if I send email or reply to email from a friend with an address similar to [email protected] I get the following message back. Have checked the address is correct and other people can send to him.

This is the mail system at host mail.enmail.co.

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

<[email protected]>: host
local-dovecot.enmail-prod.svc.cluster.local[10.98.200.172] said: 550 5.1.1
<[email protected]> User doesn't exist: [email protected] (in
reply to RCPT TO command)

[#2]

Seeing this email is being sent via the Greenby email system ( mail.enmail.co ) 
this would also be a topic to raise as a Greenby support ticket.

In that ticket be sure to post in everything un-redacted so support can see exactly what is failing. 

[#3]

This post from a few days back encountered the same error but for an ic24.net destination.

https://community.plus.net/t5/Email/Undelivered-Mail-Returned-to-Sender-with-email-ending-ic24-net/t...

[#4]

@CWatters 

Have you posted redacted returned email to postmaster@destination with query?

Possible DNS issues, unable to correctly translate from email address to IP address for some reason?

Can you ping or tracert to the destination mail server?