Goto ACP>>Maintenance>>Forum Logs>>Error Logs
see what error it shows.
Or chk the images below that you have the same settings.
General Settings.
SMTP Settings
If still no success than try to Setup an SMTP for mails.
If you use Google Apps Mail or a Gmail address for your board contact and you want to use SMTP instead of the built-in PHP mail(); function, which has many limitations.
Requirements:
1. fsockopen
2. OpenSSL
3. Google Apps Account or gmail Account
If you are unsure if you have fsockopen or Open SSL compiled with your version of PHP, go to
ACP > System > PHP Information.
Go to ACP > E-mail Settings
-- SMTP settings --
Use SMTP server for email: Yes
SMTP server address: ssl://smtp.gmail.com or ssl://smtp.googlemail.com
SMTP server port: 465
Authentication method for SMTP: PLAIN
SMTP username: username@yourdomain.com (if using Google Aps), or
username@gmail.com (if using Gmail)
SMTP password: <your password>
Click submit and you’re done!
Let me know if this tutorial helped you.
Credits to Highway of Life for the above tutorial