Lot of Delivery Status Notification Failures

[#1]

I'm not an expert on these things so please bear with me...

I use plusnet email via Outlook to receive emails only. Over the last 2 days I have received loads of DSN failures - all from Hotmail addresses and all being sent alphabetically.
All are being returned to a plusnet address that isn't one of my names but has my address after the @ (eg: aaaa@******.plus.com )
Why is this and what can I do to stop it?
Many thanks
EDIT - all the emails have 2 attachments - one a dat file and the other a message file - all titled " **** sent you a message" - I haven't clicked / opened either of these.

[#2]

Thanks for getting in touch chromium05,
I can see that you have the "Catch All" feature enabled on your mailbox.  This will mean that you can receive email from:
<ANYTHING>@username.plus.com
And as such is open to Spam of this nature.  If you were to disable the "Catch All" feature you would only receive replies from:
<mailbox name>@username.plus.com
and this would stop the messages all together but it would mean that this address alone would be valid.  You can make the changes here:
https://portal.plus.net/my.html?action=myemail&s=1&redirected=yes&?membermenu=emailsettings
by clicking:

• Manage My Mail


• Catch All Tab


• Set Catch All to "Off" and click "Submit"

You can then check the mailbox name (and email address) you should use on the "Mailboxes" tab.  Please let us know if you have any issues.

[#3]

but you should set up a mailbox for postmaster as well or you wont see the official mail, like new features, or bills due