Re: `user-mail-address' for message-ids

[Kai.Grossjohann@CS.Uni-Dortmund.DE (Kai Großjohann)]

On 27 Feb 2001, Jason R. Mastaler wrote:

> You are certainly entitled to your opinion, but two of the above
> three arguments are just that.  There are benefits to others besides
> yourself, and I'm still not convinced that my suggestion has any
> *practical* drawbacks or adds any risks.

The problems I envision stem from lots of people using `@hotmail.com'
message ids.

As the number of people with the same right hand side increases, the
risk of having a clash in the left hand side increases more than
linearly.  (Not sure if it's exponentially.)  Even though there are
365 days in a year, just a handful of people (maybe 7, maybe 13, maybe
14, not sure) are enough to give a more than 50% chance of two of them
having the same birthday (maybe in different years).  You might want
to use this for little bets at parties...

The chance of two people having the same birthday is one in 365.  The
chance of any two people in three having the same birthday is 3 in
365 (one in 365 for Peter and Paul, 1/365 for Paul and John, and 1/365
for Peter and John).  The chance for such a pairing in four people is
... hm.  There is a 3/365 chance for Mary to have the same birthday as
one of Peter, Paul, or John, and a 3/365 chance for any two of the
guys having the same birthday.  So now we're up to 6/365.  And then
12/365 (for five), and 24/365 (for six), and 48/365 (for seven).  So
nine or ten people should be enough.  Any error in my calculation?

So the chance really does grow exponentially.

So even though the chance of a clash between two specific Hotmail
users is small, the chance of a clash between _any_ two Hotmail users
is quite large because there are so many Hotmail users.

Message ids need to be unique for two years.

Also consider the huge volume of messages passing through Usenet every
day. 

kai
-- 
Be indiscrete.  Do it continuously.