Well, "a lot" could mean a multitude of things. For a frustrated user, 5 e-mails can equate to "a lot".
Anyways, go to:
AdminCP -> Scheduled Tasks -> Scheduled Task Manager.
Search for, "
Birthdays" and tell me what you see to the left of it. There should be some numbers. A screenshot is preferred.
Also, just in case you may have played around with those settings, navigate to:
AdminCP -> Scheduled Tasks -> Scheduled Task Log, and set these filters:
Log Entries to Show Per Page - 100
Show Only Entries Generated By - Birthday
Order By - Date
... and post a screenshot of what comes up.