Undelivered Mail Returned to Sender

[#1]

I got and email with subject: Undelivered Mail Returned to Sender

From:    Mail Delivery System <MAILER-DAEMON@smtp-auth-out-04.cmp.livemail.co.uk>

The content reads:

This is the mail system at host smtp.livemail.co.uk.

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

<ls-treeman@hotmail.co.uk>: host eur.olc.protection.outlook.com[104.47.12.33]
    said: 550 5.5.0 Requested action not taken: mailbox unavailable
    (S2017062302). (in reply to RCPT TO command)

Can anyone explain what the problem is and how it can be resolved?

[#2]

@ChristopherW 

550 5.5.0 Requested action not taken: mailbox unavailable

that error means the destination mailbox doesn't exist

[#3]

@ChristopherW Did you send an email to 'ls-treeman@hotmail.co.uk?

I doubt it, which means your address has been used as the 'from' address by someone sending out (I suspect) spam mail.

As a first step, I suggest changing your email password - if this is also your PN account password, change it there first.

Edited in view of reply below.

[MisterW]

Thanks MisterW and noted.  However I'm using the email address from an advertisment in the current issue of our parish magazine !  I'll try the phone number!

[#5]

Thanks John.  Yes it was an email address in an advertisment as mentioned in my reply to MisterW.  Now I've seen your editing - thanks.

[#6]

Confession time and poblem solved.  I had misread the advertisment. It was not a hyphen in the email address but an undercore 🙃 !!!  I sent a text to advertiser and he pointed out the mistake.

[#7]

These things happen.

You might pass on to the gent that his FB page offers no information about his working locations.