Ken
RE the to address not matching.
The specifics of how an email is routed to you are always in the header. On some email readers it is either difficult or nearly impossible to easily read the original text with the header info.
On some you can look for a button or menu choice for “show all headers” or “show original” which will open up the message and convert the html to text (with codes) and usually show the header information.
Most modern email clients will strip out the original header info when forwarding a suspect email to some one else for analysis, but you could try sending me one of them to check.
Here are some links to explanations that may help you understand what you are seeing if you can get a look at the headers. Some may also have outdated info on other topics related to their local mail system or historical anti spam tactics that are now obsolete, so use them for education in a general way.
http://www.windowsecurity.com/articles/Email-Spoofing.html
http://www.colorado.edu/CNS/email/headers.html
http://copland.udel.edu/~sbunting/invtips.htm
http://www.rickconner.net/spamweb/notmyaddress.html
http://www.rickconner.net/spamweb/index.html
The comcast issue can probably be easily traced but most of the comcast people I have ever talked to have no idea how any mailserver works ,let alone theirs. Most will deny that their outgoing servers use “Pop before SMTP” as an anti spam strategy even though telneting to their mail servers and testing it will show it unequivocally.
I never used a comcast email address when I had their service, (even though they gave me one or more) since I have my own mail servers, but if I remember correctly that had a way to assign multiple usernames to one actual email address.
Also if you are both using the same email address with a client set to use POP mail (which downloads the mail to your computer) with out the setting on one of them to “leave mail on server” then which ever machine checks the mail first in each cycle, will download all the incoming mail up to that point. This is useful for road warriors who wish to read their incoming mail while on the road and yet preserve it so it can be downloaded to their home or office computer for archiving. It is also possible to have one computer checking mail for two addresses while another only checks one address.
It is also possible to create this situation on an IMAP server-client but it takes several wrong settings on both sides If I remember correctly.
I am still working on my server rebuild /redesign project at the moment but I will check back in here later.