Laravel, Swiftmailer and Uncaught Swift_TransportException

Writing PHP applications that deliver email notification helps to build a versatile system that uses the most basic communication media on the Internet. The Email.

Getting the Email out would require knowledge of the Email server in use to deliver 1 or thousands of email notifications. Common Email use SMTP, sendmail, postfix or a custom Transport implementation for corporate use. There are security and reliability concerns when passing to any Email server. Some of which include protection from email header injection attacks, MIME compliant, HTML/multipart emails, inline or embedded images.

Swift Mailer helps to handle most of these things. Why reinvent the wheel? In order to use it, the application should support PHP 7.0 or higher. Installation through Composer simplifies the whole process.

$ composer require "swiftmailer/swiftmailer:^6.0"

More details are found at Swift Mailer.

Purpose

Back to the original reason of this post. On a recent Laravel application, tested was carried out and checklist done on Centos Linux development server However when deployed to production Centos Linux server, email notification produced following error;

PHP Fatal error: Uncaught Swift_TransportException: Connection could not be established with host EMAILSERVER_NAME[Permission denied #13]

The full error is shown below.

[Thu Aug 30 14:35:54.225637 2018] [php7:error] [pid 18234] [client IPADDRESS:32852] PHP Fatal error: Uncaught Swift_TransportException: Connection could not be established with host EMAILSERVER_NAME[Permission denied #13] in /var/www/tboxmy/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Transport/StreamBuffer.php:277\nStack trace:\n#0 /var/www/tboxmy/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Transport/StreamBuffer.php(62): Swift_Transport_StreamBuffer->_establishSocketConnection()\n#1 /var/www/tboxmy/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Transport/AbstractSmtpTransport.php(113): Swift_Transport_StreamBuffer->initialize(Array)\n#2 /var/www/tboxmy/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Mailer.php(79): Swift_Transport_AbstractSmtpTransport->start()\n#3 /var/www/tboxmy/public/info/testemail.php(21): Swift_Mailer->send(Object(Swift_Message))\n#4 {main}\n thrown in /var/www/tboxmy/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Transport/StreamBuffer.php on line 277 

 Solution

I am sure there are other possible ways to get this error, but in my case it was SELINUX. On the development selinux was on permissive and on production it was enforcing (quite strictly).

The next time this happens; here are the steps to take.

Determine selinux status and the booleans.

$ sestatus
. . .
$ getsebool httpd_can_sendmail
httpd_can_sendmail --> off
$ getsebool httpd_can_network_connect
httpd_can_network_connect --> off

Turn the permission to ON.

$ sudo setsebool -P httpd_can_sendmail 1
$ sudo setsebool -P httpd_can_network_connect 1

Restart the web server.
Done.