550:550 The sending IP (220.127.116.11) is listed on https://spamrl.com/. Please resolve this and retry.
The issue of one of Virgin Media's outgoing email servers appearing on spamrl.com's 'blacklist' has come up a few times before. One of the Forum Team (VM employees) who support this forum will pick this up and pass it on to the appropriate VM IT team. They are the only people who can get the listing removed. One of the Forum Team will contact you via this forum in the next day or so.
In the meantime, the fact that the email is going through one of VM's UK based servers shows that you sent it via an email app or client (such as Outlook). The VM webmail service uses VM 's servers in the Netherlands and so you should find that you are able to successfully email this contact by sending a message from your account using VM Webmail https://mail2.virginmedia.com/
One other thing. Despite the bounce message saying that delivery failed, do you know whether your contact actually received the message?
The reason i ask is that I have noticed with other cases that the information in the spamrl.com link in the bounce message https://spamrl.com/ actually says:
"Although you received a bounce message indicating the email was not delivered, your email was actually NOT discarded! The antispam provider of the recipient safely stored a copy of your email in the spam quarantine system of the recipient."
"Although it was rejected with a 5xx error at SMTP level, they really can still access and release & train the email from their quarantine."
I must admit, I am very sceptical about both those statements but all I can say is that is what Spamrl themselves actually say. So it might be worth checking with your contact (perhaps via an email from Webmail) whether your original email arrived in their spam folder.
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