Tentative d'infection ?

Bonjour,
J'ai reçu hier soir les 4 courriels suivants :

1 / de : "Mail Delivery Subsystem" <MAILER-DAEMON@smtp32.msg.oleane.net>
The original message was received at Sun, 22 Nov 2009 22:25:23 +0100
from localhost [127.0.0.1]

----- The following addresses had permanent fatal errors -----
<amturon@cg32.fr>
(reason: 550 Mail rejected - identified as SPAM with score Confirmed)

----- Transcript of session follows -----
... while talking to [81.252.124.93]:
>>> DATA
<<< 550 Mail rejected - identified as SPAM with score Confirmed
554 5.0.0 Service unavailable

2 / de :"Mail Delivery System" <MAILER-DAEMON@mx.uol.com.br>
This is the mail system at host starfury27.uol.com.br.

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

<amtveiculos@uol.com.br>: host mfuol.mail.sys.intranet[172.27.64.15] said: 550
RCPT TO:<amtveiculos@uol.com.br> User unknown (in reply to RCPT TO command)

3 / de : postmaster@bms.dk
Your message has encountered delivery problems
to the following recipient(s):

amtup2003@bms.dk
(Was addressed to amtup2003@bms.dk)
Delivery failed
550 amtup2003@bms.dk... No such user

No recipients were successfully delivered to.

4 / de : "Mail Delivery Subsystem" <MAILER-DAEMON@singnet.com.sg>
The original message was received at Mon, 23 Nov 2009 05:25:19 +0800
from mx17.singnet.com.sg [165.21.74.117]

----- The following addresses had permanent fatal errors -----
<amtute@singnet.com.sg>
(reason: 550 5.1.1 User unknown)

----- Transcript of session follows -----
550 5.1.1 <amtute@singnet.com.sg>... User unknown

Je soupçonne fortement une tentative d'infection et/ou d'hameçonnage, car je ne connais pas toutes ces coordonnées.
De plus, je ne constate actuellement aucune anomalie dans mon système.
Je précise que je n'ai pas importé ces 4 courriels dans Thunderbird ( juste consultés sur le serveur Orange ).
Pouvez vous SVP m'éclairer ?
Merci d'avance.