What is causing Mail to send me e-mail out of my own inbox/sent folder

Question

I don't really know how to easily describe this, but here goes.  This started yesterday. I get a message in my inbox from a previous e-mail correspondent. When I open the message it is actually an old message from in my inbox or sent folder that is not to (or from) the person that supposedly sent me the current mail.  It could be to me from a completely different source or it could be from me to a completely different recipient.  What could be causing this?
I have an iMac 22.5 inch running OSX 10.7.3
I loaded ClamXav and ran it.  It found two threats and isolated them.  I saw those threats in other posts and I think they are benign.  The files are two .emlx files.  they are identified as phishing threats.
I previously was infected with the Flashback Trojan but found it and performed the Apple OS update.  I have since changed all my passwords, but I am still getting these funky e-mails.  This afternoon I received a reply from a correspondent.  When I opened the reply, it was an actual reply, but in the thread it had an e-mail I had received a year ago from a banking site with registration information embedded in the thread!   The correspondent didn't mention this, so I don't think she saw it.  When I replied back the embedded bank e-mail was gone from the thread.  I've searched through support and I don't see anything like this.
Very strange -

Answer 1

rdog2 wrote:
I think the virus thing is a red herring.  ClamXav identifies the threats as:
Heuristics.Phishing.Email.SpoofDomain
The "Heuristics" label means that nothing in the message positively identified it as a phishing attempt, but something about the way links were formatted within the message made it look suspicious enough to warn you that it might be. Those are the messages that usually need to be read first to make certain they aren't something you need to keep.
I don't know how to find the offending files now anyway.  The window that came up and told me the two infected files in ClamXav is gone, and when I try to go to the logs it shows every file searched.  Knowing the first file was 6-something-something.emlx allowed me to narrow it down until I found the entry in the log, but I don't remember the other file.  And how do I go to my inbox and find 686.emlx in order to open it and put it in the trash.  Maybe I can open it from finder.
It's possible that those two messages were already in your Junk or Trash mailboxes and have been deleted already, so that's why they aren't being detected any more.
To find those entries in your scan log, type Command-F to bring up the find dialog, enter "FOUND" without the quotes in capitol letters in the "Find:" box and un-check the "Ignore Case" box. Only that most recent part of the log is visible in the window, so if you don't find them at first use the "▲ Earlier |" button in the lower right hand corner of the log window to see more. That should tell you the path to where that message was at the time. Probably something like:
~/Library/Mail/<mailaccountname>/INBOX.imapmbox/Messages/
where "~" is your home folder at /Users/<yourusername>/
If and when you find the file, just double-click it to open it in Mail and decide what you need to do with it.
Anyway, I don't think this has ANYTHING to do with the problem I was having
Agree.