Spam?

I've recently received several strange emails that seem to be in response to emails that I don't remember sending and to addresses that I don't recognize. One of those emails was to five aol.com addresses that I don't recognize. I've listed the emails below. They all have attachments, which I haven't opened. These emails were captured by my Earthlink spam filter. I'm not worried about the emails themselves, but I wonder if my computer could be sending spam? Thanks, Caoim

From: Mail Administrator <Postmaster@bellnexxia.net>
To: (me)
Subject: Mail System Error- Returned Mail
Date: Dec 17, 2009 2:01 PM
Attachment: "unknown-351 B Forwarded-Message"

"This Message was undeliverable due to the following reason:
Each of the following recipients was rejected by a remote mail server.
The reasons given by the server are included to help you determine why
each recipient was rejected.
Recipient: <eschalon@speedfactory.net>
Reason: Unrouteable address"
---------------------------------------------------------------

From: postmaster@g4s.com
To: (me)
Subject: Delivery Status Notification (Failure)
Date: Dec 17, 2009 10:46 PM
Attachment: "unknown-264 B Forwarded Message"

"This is an automatically generated Delivery Status Notification. Delivery to the following recipients failed.
emmerich.kirchseeon@t-online.de"
-------------------------------------------------------------

From: Mail Delivery Subsystem <MAILER-DAEMON@mb2d60.vdrs.net>
To: (me)
Subject: Warning: could not send message for past 3 hours
Date: Dec7, 2009 10:35 AM
Attachment: "unknown-290 B Forwarded-Message
********************************************
THIS IS A WARNING MESSAGE ONLY YOU DO NOT NEED TO RESEND YOUR MESSAGE **********************************************
The original message was received at Mon, 07 Dec 2009 22:35:17 +0700
----- The following addresses had transient non-fatal errors -----
<boxers4355@aol.com>
----- Transcript of session follows -----
Warning: message still undelivered after 3 hours
Will keep trying until message is 1 days old
---------------------------------------------------------------

From: Mail Delivery Service <postmaster@cp-out10.libero.it>
To: (me)
Subject: Delivery Status Notification
Date: Dec 8, 2009 6:37 AM
Attachments: unknown-290 B Forwarded-Message

"The original message was received at Tue, 08 Dec 2009 18:37:54 +0700
----- The following addresses had permanent fatal errors -----
<boxers4355@aol.com>
----- Transcript of session follows -----
554 could not connect and send the mail to mailin-01.mx.aol.com
-------------------------------------

From: postmaster@in.g4s.com
To: (me)
Subject: Delivery Status Notification (Failure)
Date: Dec 17, 2009 10:50PM
Attachment: unknown-698 B Forwarded-Message

This is an automatically generated Delivery Status Notification.
Delivery to the following recipients failed.
vweisel@aol.com
ukpaulturner@aol.com
tucson827@aol.com
terenial8305@aol.com
percyjojo@aol.com
Confidentiality Notice:
The information contained in this electronic message and any attachments to this message are intended for the exclusive use of the addressee(s) and may contain confidential or privileged information. If you are not the intended recipient, please notify the sender at admin@in.g4s.com immediately and destroy all the copies of this message and any attachments
--------------------------------------

From: Mail Delivery System <MAILER-DAEMON@lamia-25.totisp.net
To: (me)
Subject: Delivery Status Notification (Failure)
Date: Dec 18, 2009 4:38 AM
Attachment: "unknown-279 B Forwarded-Message"

The following message to <eschalon@speedfactory.net> was undeliverable.
The reason for the problem:
5.1.0 - Unknown address error 550-'Unrouteable address'