I THINK I'VE SENT A VIRUS BY EMAIL:

The new breed of virus infections will sometimes infect a PC or server and scan those machines for email addresses. These can come from Outlook Address books, personal address books, temporary internet files, just about any source that can contain email addresses.

Newer virus infection will then either:
1. Send out emails to those addresses with the virus as an attachment in the hope the attachment is opened and the virus infection will spread to new PC's / Servers where the process will start again.
2. The virus will fake (or spoof) the senders email address to match something it has found whilst scanning for email addresses. That way, if a user replies the virus originator is not so easily detected.

DO NOT assume it was you that sent the virus !! Check your sent items and see if there are any unusual email in there (the chances are there will not be). Ask your system administrator to check your servers email application (if used) for any unusual outbound messages (again, the chances are there will not be any).

If you have an Anti Virus applciation installed then it makes it highly unlikely it was you that sent the email. As explained above, some viruses will add a fake 'from' and 'return address' to emails they send out from other peoples computers, although your email address shows as the sender you will have a clean PC, no virus infection, it is more than likely someone you have sent emails to that has your email in their address book.