"Mail delivery failure"

[#1]

Over the past few weeks I have started to receive on an irregular basis large numbers of emails reporting "mail delivery failure" from supposed recipients to whom I have not sent an email in the first instance.  These in the main come over night from "au" addresses.  On 3 Feb I received over 200 and on 4 Feb I received 404.  I have reported these as spam which will catch some but there is a real danger of posting accidentally genuine senders emails to spam.  In the meantime  these should arrive at my outlook in the Junk mail folder.
I have increased the spam setting on my account with little or no effect.
Are you aware of this problem and if so what, if anything, can be done about this problem.  Will it go away - I suspect not
Regards
Richard Vaughan

[#2]

Hi Richard,
I've replied to your private message, but for the benefit of others:

Quote from: richardvaughan

Will it go away.

Yes. It's a royal nuisance but it will stop eventually. There's not a huge amount you can do in the meantime other than ride it out.

[#3]

For the past 6 months I have the same in all three of my boxes. I have made mail rules that send these to the junk folder and then are deleted 7 days later. However I am heartily sick of seeing them download. Using the subject line of the message source as the filter works until new variants of the subject are delivered then I have to add them into the rules.
If we just have to 'ride it out' until it stops then why when I had an online chat with a colleague of yours Bob, did he advise me to change my password? He more or less said that someone could have access to my account.
I did as advised and surprise! surprise!....................I still receive them.
Since when do people need my password to send me mail?? 
Clearly even though some purport to come from me-others have a blank <> as the 'from' field- they are spoofed. I have searched around forty blacklisting sites and in four of these my mail is now blacklisted on two of my accounts. Fortunately (as far as I can tell) it has not impacted on my use of the accounts(yet).
I switched on the spam filter so now I'm getting these also to add to the bloat of mail. 

[#4]

Quote from: cnitall

If we just have to 'ride it out' until it stops then why when I had an online chat with a colleague of yours Bob, did he advise me to change my password? He more or less said that someone could have access to my account.

Possible, but unlikely. The headers in the returned emails would tell you whether or not they were sent from Webmail/via Plusnet's servers (which would be the case if somebody were abusing your account).
Six months is a long time to be receiving such messages, but if the cause is what I suspect then there really isn't a great deal that can be done