In version 3.4 when I Approved All Pending Members the email was not sent. However when I Approved Selected Pendin Members (ie; those I had checked) the email was sent.
I seem to remember an earlier post about this indicating this would be fixed in 3.4.01 but cannot seem to find it.
However, now when I approve pending members by both means neither sends an email.
I think the problem lies with CDOSYS support in 3.4.01. I've been checking the code and it didn't look wrong anywhere. I also noticed that the send email to friend feature was not sending email, either. So I changed the email component from CDOSYS for JMail and verified everything is working.
Conclusion: the problem must be changes introduced(?) in CDOSYS support in 3.4.01.