socket

[Gustavo Cordova]

> 
> Nothing evil here.  I have 2 reasons why I would do this 
> program.  Firs, it is my TCP/IP concept class's project.
> Basically, I want to try what the book tells in to code,
> but I notice it does not work the way it says in so many
> commercial SMTP servers.  Second, I have been unemployed
> for about 4 months.  My friend's company needs a program
> to verify the users who registered to their service.
> They found out many registered users were using fake addresses.
> I just want to try this program to see if I will get
> a job there.  That's all!  I really do appreciate if you 
> would provide any info for me to complete this project.
> 
> Thanks in advance!
> 
> Billy Ng
> 

Use a two-phase subscription method:

1. User subscribes.

2. Server intercepts the subscription mail, and bounces
   a confirmation mail to the sender.

3. User replies to confirmation mail.

4. Server intercepts confirmation mail, and processes any
   opaque information there; which normally means that it
   retrieves a data value from a pending-subscriptions database
   and finishes processing the subscription request.

5. Server dispatches finalization email to subscribed user.


Now you don't need to hack on VRFY, which was a nice idea,
but spammers and email-address-harvesters don't play nice,
which is why it's either not used, or permanently wired to 1.

Salutations!

-gustavo