Transistor Rhythm. Dude.
KEEP YOUR MOUTH SHUT about it. Trust me. Been in a similar situation, it didn’t end up well when I thought that the right thing to do was to bring it up. It wasn’t weird before, then it became weird in my effort to make sure it wasn’t weird.
Those are my two pennies about it. Good luck.
I started a thread about this not too long ago to find out how normal it is to kiss friends of the opposite sex. It turns out that a few of us are ok with it while many others find the idea to be a little gross.
I kiss many of my opposite sex friends goodbye, and occasionally hello if we haven’t seen each other in a long time. To us, it’s perfectly normal - it’s our way of showing our close friends that they are special. The kiss is affectionate, but not sexual.
The fact that she acts like it’s normal tells me that she simply meant to show you how happy she was to see you, but nothing more should be implied. You should take it as a compliment and nothing more. Like others said - don’t make a big deal out of it because it wasn’t a big deal. If you do you will only make things awkward between you.
Update: Right when I decided to just keep mum about the whole thing, she e-mails me and says that she’s “felt the same way about me” for the past year, but that we “shouldn’t jeopardize anything” and so let’s just pretend that it never happened.
A little 
, but more :smack:
Dinsdale nailed it, then. 
I just sprang a little bit of vicarious wood.
If you value your friend, you’d take her advice.
Especially since some people have no better sense than to write emails about stuff that never even happened!
+1
Sage wisdom indeed.
On the other hand: Friends, Schmends.
vicariously, +1
face it, the cat will not go back in the bag.
And delete the e-mail! Like right now!
Have you seen her husband since the kiss? If she thought something weird had happened, she would’ve told her husband. I’m assuming if her husband thought you were poaching, he would have had it out with you by now, correct? So, if it wasn’t important enough to bring up to the husband and/or wasn’t important enough to take up with you, it’s not an issue in general and you should just let it go.
For me, the telling thing in the OP was how “overjoyed” he was at seeing her.
“Overjoyed”? “Happy” is one thing, but I have to honestly say that I have never felt “overjoyed” at seeing a friend’s wife (or a female friend of my wife’s, for that matter) unless she was so incredibly attractive that, even knowing that nothing would ever happen between us, just having her around brought my testosterone up to a pleasantly full boil.
I also have never “accidentally” kissed any woman on the mouth. Ever. Every woman I’ve ever kissed on the mouth (regardless of whether it was reciprocated or not), I kissed on the mouth because I wanted to kiss her on the mouth.
“Oops” indeed.
He pretty much has to.
Forward the email to her husband after you bang her.
The next step is tell. You just did that. Don’t bring it up in the future. This incident needs to be buried.
I’d like to know where these women friends are who kiss full on like OP describes. It has never happened to me. A peck on the cheek or maybe a peck on the lips, not not this.
“I wouldn’t worry about it unless you find yourself sporting wood whenever you think about the kiss”
If “the kiss” happened to me, I don’t think I would be able to avoid sprouting one.
Delete the e-mail and burn the computer.
You really only have two choices. 1) you chalk it up as one of those flukes in the time-space continuum and go on about your business, or 2) you pursue it.
If you go with option 2, there are several outcomes, and unless you’re living in a Noel Coward drawing-room comedy, none of them are pretty.
You really need to go kiss your friend, just to balance things out.
Was she wearing pyjama pants?