1. Have you updated to 1.5.2?
2. Do you use SMTP?
3. Is your CRON set?
4. Did you use real email under settings> main settings
a) go to your database>>find "ow_base_mail" table. Check whether it contains any mails that are "to be sent"
b) try to register as a new user. send yourself a verification emails
c) refresh "ow_base_mail" table. Was your latest email added to the list?
d) wait until CRON runs or run it manually, check the table again, did the latest email disappeared from the list within the table ?