Ive been getting an awful lot of these too over the past few months.
They are sent to <every name under the sun>@my domain, and they're obviously malicious
In my case its where someone has attempted to spoof my email address to send malicious mail to somewhere else. When they fail they end up bouncing back to me - even though I never actually sent them.
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Historically this type of spam usually starts not by you having a virus, but someone who has your email address in their records getting a virus. These type of viruses have an SMTP engine, that specifically look on an infected machine for email addresses. The typical way it may picks up email addresses is by scanning any mail on the system and looking for new addresses in the CC field. From the smtp engine it then sends out a zillion further emails spoofing the chosen email address.
This is why I am so against people using CC when they send out joke type emails to everyone on their friends list. A friend of a friend is the likely culprit who has the virus, but the virus uses your email address simply because your friend has used the CC field which displays your email address to all and sundry.
The newer type smtp viruses go one step further and will also dictionary spoof the first part of a domain.
Its a big rant of mine.
1)
Dont use CC (use BCC) 2)
Dont bounce mail - it never to goes back to the right place & some innocent sod usually gets it.