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Emailqueue

Almost anyone who has created a web application that sends emails to users in the form of newsletters, notifications, etc. has tried first to simply send the email from their code using the PHP email functions, or maybe even some advanced emailing library like the beautifully crafted PHPMailer (https://github.com/Synchro/PHPMailer). Sooner or later, though, they come to realize that triggering an SMTP connection from within their code is not the most efficient way to make a web application communicate via email with their users, mostly because this will make your code responsible about any SMTP connection errors and, specially, add all the SMTP delays to the user experience.

This is where solutions like Emailqueue come in handy: Emailqueue is not an SMTP relay, and not an email sending library like PHPMailer (though it uses PHPMailer for final deliver, actually). Think of it as an intermediate, extremely fast, post office where all the emails your application needs to send are temporarily stored, ordered and organized, this is how it works:

Your application needs to send an email to a user (or 10 thousand emails to 10 thousand users), so instead of using the PHP mail functions or PHPMailer, it simply adds the email to Emailqueue. You can add emails to Emailqueue by injecting directly into Emailqueue’s database or using the provided PHP class.

The insertion is made as fast as possible, and your application is free to go. Emailqueue will take care of them.

Every minute, a cronjob calls the Emailqueue’s delivery script, completely appart from your running application. Emailqueue checks the queue and sends the queued emails at its own pace. You can configure a delay between each email and the maximum number of emails sent each minute to even tune the delivery speed and be more friendly to external SMTPs.

Emailqueue even does some basic job at retrying emails that cannot be sent for whatever reason, and stores a history of detected incidences.

Sent emails are stored on emailqueue’s database for you to check who received what. A purge script can be regularly called via cronjob to automatically delete old, already sent emails to avoid your emailqueue database grow too big.

Best features

• Inject any number of emails super-fast and inmediately free your app to do other things. Let Emailqueue do the job in the background.

• Prioritize emails: Specify a priority when injecting an email and it will be sent before any other queued emails with lower priorities. E.g: You can inject 100k emails for a newsletter with priority 10 (they will take a while to be sent), and still inject an important email (like a password reminder message) with priority 1 to be sent ASAP even before the huge newsletter has been sent.

• Schedule emails: Inject now an email and specify a future date/time for a scheduled delivery.

• The code is quite naive, built about 15 years ago. But boy, it’s been tested! This means it will be very easy for you if you decide to branch/fork it and improve it. Emailqueue is a funny grown man.

Caveats

Since the delivery of the emails is triggered via a cronjob, and the fastest rate at which a cronjob can be fired is once per minute, emails sent with Emailqueue may take up to 1 minute to be finally delivered.