Probably not. As it turns out, it's very easy to spoof e-mail headers.
The "From" address in the message headers is the digital equivalent of the address typed in the upper right corner of an ordinary paper letter. You can type anything you like there. Canada Post doesn't open the envelope to check it. So I can write
Santa Claus
1 North Pole Plaza
H0H 0H0
Jan. 18, 2038
Huckleberry Hound
Pooch House
Ottawa, ON
K9K 9K9
Dear Huck,
Don't bother trying to be good this year. I've already decided
you're getting a lump of coal.
Yours truly,
S. Claus
Then I can put it in an envelope:
+---------------------------------------------------------------+
| Barack Obama +-------+ |
| 1600 Pennsylvania Avenue NW | stamp | |
| Washington, DC 20500 | here | |
| U.S.A +-------+ |
| |
| The Right Hon. Stephen Harper, MP, PC |
| 24 Sussex Drive |
| Ottawa, ON |
| K1A 0A3 |
| |
+---------------------------------------------------------------+
and Canada Post will deliver it to the Prime Minister's residence. If they can't deliver it, they'll try to return it to the U.S. president's residence. All this without anybody stopping to ask for proof that I really am Barack Obama, or that I really am Santa Claus.(What makes spam so popular is that nobody asks for a stamp.)
E-mail works the same way. It's possible to trace the path that a message took on its way from sender to recipient, but it's not possible to verify the identity of the sender. Sometimes this may even be legitimate. While visiting a friend in Russia, I may want to send myself an e-mail reminder when to do something when I get home, so I ask my friend to let me use his e-mail client to send myself a reminder. In such a case, it makes sense for me to set both the "From" and "To" address to my own.
Most of the time, of course, when this happens, it's because a spammer is spoofing mail addresses. Don't worry about it; it's all automated, and they haven't broken into your account or anything like that. Their program just says "Use the same address for To and From".
