Vbulletin emails not working
 

Hi all guys,
I have a new problem on my VBulletin 3.8.2
After updating from 3.8.1 PL1 new registered members cannot receive activation email from forum. I tried with the ad-hoc section on admin panel to send an email to my address but he found no problems.

Anyway mails don't arrive and i haven't got anti-spam filters. I tried with many email addresses but as i can see many new user have my same problem too. I use mail() PHP function to send mail, and not SMTP.

What can i do?
Thanks in advance