From phpBB Development Wiki
Diagnosing and resolving issues related to outgoing email in phpBB.
You need to know what your email settings are, and you might need to change them.
The settings are located in ACP -> General tab -> Client communication -> E-mail settings.
The first step is looking in the error logs for any recorded error(s).
The error log is located in ACP -> Maintenance tab -> Error log.
No Error Message
If you see the following:
and your email settings are configured to use PHP mail function, change your email settings to use SMTP to localhost (see the next section) and try sending email again. If it works - great, you are done. If it does not work check the error log and you should see an error message this time.
SMTP to localhost
Go to email settings (see above for the location) and set parameters as follows:
- Use SMTP server: Yes
- SMTP server address: localhost
- SMTP port: 25
Leave SMTP username and password empty.