Virusinfected? Outlook seems to send out mails with attachment

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My landlady's Outlook receives up to 20 mailer-daemon messages saying
that an email sent from her computer bounced because the address was
wrong. The interesting thing is she never sent these emails. The
emails have an attachment of about 100 kB, so this gets to be quite a
problem.
We tried to change the account but lo and behold the problem remains.
Is Outlook infected, or the underlying files (like winsock or what it
is called)?
Does anyone know what this is?
Håkon

 

[Brian Tillman]

My landlady's Outlook receives up to 20 mailer-daemon messages saying

that an email sent from her computer bounced because the address was
wrong.

Two of the more likely causes: 1) some SPAMmer has hijacked her address and
is sending out SPAM, spoofing it to look like it comes from her. 2) Someone
she knows and who has her address in their address book has a trojan horse
program on their computer and that computer is sending out the messages,
using her address (and other from that address book) as the From address.

We tried to change the account but lo and behold the problem remains.

Do you mean you closed down her old account and opened another for her with
a different address?
--
Brian Tillman
Smiths Aerospace
3290 Patterson Ave. SE, MS 1B3
Grand Rapids, MI 49512-1991
Brian.Tillman is the name, smiths-aerospace.com is the domain.

I don't speak for Smiths, and Smiths doesn't speak for me.

 

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Thank you for your answer.

Two of the more likely causes: 1) some SPAMmer has hijacked her address and
is sending out SPAM,

This is unlikely, since the same problem surfaced after we changed to
a whole new POP account.

spoofing it to look like it comes from her. 2) Someone
she knows and who has her address in their address book has a trojan horse
program on their computer and that computer is sending out the messages,
using her address (and other from that address book) as the From address.

That may be.

Do you mean you closed down her old account and opened another for her with
a different address?

Yes. Well, we did not close the old account, but certainly opened a
new one. Could it be that her internet IP software is affected by a
virus that detects her address and sends out these messages?
Håkon