The same thing is happening to me.
After 10 people successfully registered for the message board, suddenly new registrants are not sent the confirmation email. I registered a 'test' member (with a unique email address) but never got the confirmation email. Nothing has changed in the configuration since people registered successfully. Any suggestions?
Template(s) used: subsilver
Any and all MODs: none
Do you use a port of phpBB: ?
Version of phpBB: 2.0.17
Version of PHP: 4.3.10
Which database server and version: MySQL 4.0.23
Host: Linux i686
Did someone install this for you/who: no, I did
Is this an upgrade/from what to what: I did a complete install over 2.0.0
Is this a conversion/from what to what: NA
Have you searched for your problem: Yes
If so, what terms did you try: register, activate, email, confirmation
State the nature of your problem: registrants do not receive the email to confirm
Do you have a test account for us: No