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.
If you have access to system email logs, you need to examine them also. To find out whether you have this access you need to ask your host. If you host the board yourself then you most certainly should have access to these logs - refer to the documentation for your email software to determine where they are located.
No Error Message
If you see the following:
and your email settings are configured to use PHP mail function (this is the same as having Use SMTP server set to No), 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.
Please see this topic for email settings to use for GMail.
Please see this topic for email settings to use with Google Apps.
Email Delay on GoDaddy
If you are on GoDaddy hosting and you are experiencing an email delay, please see this topic.
At this time STARTTLS is not supported by phpBB for sending email. With STARTTLS the connection begins as a plain text connection over port 25 and is then switched to SSL/TLS while continuing operating over port 25. phpBB only supports SMTPS, where the entire conversation must be encrypted with SSL/TLS from the start. Usually SMTPS operates on higher ports like 465.
Only Mass Email Is Not Working
Currently phpBB mass email code, when not using SMTP, is incompatible with some sendmail configurations. If email is working for notifications but not for mass email, and you are not using SMTP, try SMTP to localhost as detailed above. For more information please see this ticket.