Goto ACP>>Maintenance>>Forum Logs>>Error Logs
see what error it shows.
Or chk the images below that you have the same 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.
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:
SMTP server address:
ssl://smtp.gmail.com or ssl://smtp.googlemail.com
SMTP server port:
Authentication method for SMTP:
SMTP username: email@example.com
(if using Google Aps), or firstname.lastname@example.org
(if using Gmail)
Click submit and you’re done!
Let me know if this tutorial helped you.
Credits to Highway of Life for the above tutorial