Why you might want to use SMTP to make emailing more reliable

Emailing from phpBB is often problematic. In a previous post I looked at various ways to make sending email from phpBB more reliable.

In this post I look at why you might want to configure phpBB to use SMTP (Simple Mail Transfer Protocol) to send emails. If you are using a Windows web server (IIS), this is usually required. You can change these settings in ACP > General > Client communications > Email settings, which can be set halfway down the page.

By default, phpBB hands off email to PHP using PHP’s mail function and hopes for the best. If the mail function returns FALSE, the email should not have gone out. You won’t necessarily be know if it fails, however. Known email sending failures appear in phpBB’s error log: ACP > Maintenance > Error log.

Even if the PHP mail function returns TRUE, it may be a false report. In many cases TRUE only means that the mail was accepted. Whether TRUE means “accepted” or “successfully sent” depends on how your host’s email server is configured.

Once accepted by the email server, the email is likely to be closely examined. If it has some of the markers of being spam, it will probably get blocked from actually being sent out. In this case, you probably won’t know about it. You can greatly improve the odds that emails will go out successfully if you:

  • Create an email account that uses your forum’s domain, ex: admin@mydomain.com
  • Assert this email address in phpBB: ACP > General > Client communications > Email settings. Set this email address for Contact email address and From email address.

By default on Linux web servers (most typical kind of hosting), PHP’s mail function sends outgoing email to a sendmail process. Essentially, emailing is the job of your server’s operating system, so you can’t control it. Because you can’t control it, sendmail will be configured generically. Any other domains on the server you are using will send email out through the same sendmail process.

However, if you use SMTP to send email instead, you have to authenticate yourself with the SMTP mail server. By properly authenticating yourself, emails are likelier to go out. The downside is that it’s a bit of a hassle to set up SMTP. I discovered this on this site when I moved my hosting to siteground.com. It uses WordPress which by default also uses sendmail. Emails weren’t going out. A call to Siteground’s tech support revealed that SMTP was a better way to go. They provided the credentials to use and now my WordPress email notifications go out quickly and reliably. This should work for phpBB too.

Don’t assume that you can use an external SMTP server like GMail. Many web hosts will block outgoing SMTP email. If it’s allowed, by all means go ahead. You should check with your web host for the proper email settings to use.

One possible downside is that outgoing email quotas are likely, but that’s probably also true if your host uses sendmail. Your web host can tell you what policies if any apply to your hosting. See the previous post for instructions on how to properly set your email package size and to set up a system cron, if necessary. Make sure it works by sending a test email, an option available on the email settings page.


If you administer a phpBB board, you should find my book Mastering phpBB Administration invaluable. Learn lots of tips, tricks and secrets I learned from serving over 400 clients. Paper and Kindle versions available.

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