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How to Migrate SwiftMailer to Symfony Mailer in Easy Steps

With SwiftMailer no longer being maintained, it’s time to transition to Symfony Mailer.

Symfony Mailer provides a modern alternative with robust features while maintaining compatibility with many existing configurations.

Today, we are going to take a closer look at how to switch from Swift Mailer to Symfony Mailer, preserving our email template functionality and SMTP configurations.

An Overview:

• Key Steps to Switch from Swift Mailer to Symfony Mailer
• Switch from Inline Styling to Libraries
• Migrate Custom Code or Multiple Mailers
• First Test Email with Symfony Mailer
• Handling Errors After the Upgrade
• Why Symfony Mailer is a Better Alternative
• Testing Email Deliverability After Migration
• Troubleshooting Common Symfony Mailer Issues

Key Steps to Switch from Swift Mailer to Symfony Mailer

1. Before making any changes, always back up our site. This ensures that we can restore our previous configuration if any issues arise during the migration process.
2. Then, ensure that we save any Swift Mailer or Mail System configurations. These will be necessary to set up Symfony Mailer.
3. Symfony Mailer cannot be enabled alongside Swift Mailer and the Mail System module. If we try to allow the Symfony Mailer Back-Compatibility module while Swift Mailer is still installed, we will receive the following error:

   Symfony Mailer Back-Compatibility Module cannot be installed with the Mail System module.”

   We can uninstall the modules like this:

   
drush pm:uninstall swiftmailer
drush pm:uninstall mailsystem

4. After uninstalling Swift Mailer, we can enable Symfony Mailer by running:

   drush pm:enable symfony_mailer
drush pm:enable symfony_mailer_bc


   Then, follow the on-screen instructions and ensure everything is set up correctly.
5. Now that Symfony Mailer is installed, use the saved Swift Mailer configurations to set up Symfony Mailer.

Switch from Inline Styling to Libraries

If we haven’t made custom changes to our themes, no additional work is needed. However, if our custom theme includes specific styling, follow these steps:

Symfony Mailer automatically removes raw CSS styling from templates, which means inline styles in `email.html.twig` or `varbase_email.html.twig` will no longer work. To resolve this, remove custom CSS from the template and attach styles using Drupal’s library system.

Here’s an example of how to attach our custom styles:

In our custom_subtheme.libraries.yml file:


default.email-style.ltr:
css:
theme:
css/theme/email-style.theme.ltr.css: {}
default.email-style.rtl:
css:
theme:
css/theme/email-style.theme.rtl.css: {}


This ensures custom styles for LTR and RTL emails are applied correctly.

In the custom_subtheme.info.yml file:


libraries-override:
varbase_email/default.email-style.ltr: custom_subtheme/default.email-style.ltr
varbase_email/default.email-style.rtl: custom_subtheme/default.email-style.rtl


This overrides the default Varbase Email libraries with our custom styles.

Migrate Custom Code or Multiple Mailers

Symfony Mailer supports custom email templates and multiple transport configurations for each module. If our old project had custom code or multiple mailers, migrate this functionality using the Symfony Mailer plugin system.

First Test Email with Symfony Mailer

Symfony Mailer comes with an integrated UI that lets us configure email settings and send test emails directly from the admin interface. We no longer need a separate mail system interface like SwiftMailer.

Then, send a test email and validate the configurations by going to /admin/config/system/mailer/test

This interface lets us:

• Configure email body, subject, and theme.
• Set policies for each email type, such as addresses (from, to), transport method, and whether the email should be converted to plain text.

Handling Errors After the Upgrade

After upgrading to PHP 8.2 and switching from SwiftMailer to Symfony Mailer, some users may run into error messages like:

Unable to connect with STARTTLS: stream_socket_enable_crypto(): SSL operation failed with code 1. OpenSSL Error messages: error:0A000086:SSL routines::certificate verify failed

This error occurs due to SSL certificate verification issues. To resolve this, disable peer verification by adding the following to our DSN query string:

'verify_peer' => 0

Disabling peer verification should resolve the SSL connection error.

Why Symfony Mailer is a Better Alternative

Symfony Mailer offers significant improvements over SwiftMailer, making it a better choice for email management:

• Unlike SwiftMailer, Symfony Mailer is actively maintained, ensuring compatibility with the latest PHP versions and security patches.
• It handles high email volumes efficiently, supports queuing, and optimizes server resources.
• Furthermore, Symfony Mailer includes advanced features like multiple transports, enhanced error handling, and better security protocols (TLS/SSL).
• It integrates seamlessly with Symfony components but can also be used as a standalone package in non-Symfony projects.

Testing Email Deliverability After Migration

After migrating, we have to test email deliverability to ensure emails are reaching inboxes properly:

• Ensure emails are rendering correctly across different clients (Gmail, Outlook, etc.).
• Verify that the domain’s authentication records are set up properly to prevent spam flags.
• Then, send test emails to various addresses and monitor delivery.
• Also, services like Mailtrap or SendGrid can simulate email environments and monitor deliverability.
• Send test emails to real inboxes to gather insights on potential issues.

Testing ensures that our emails are delivered without issues and remain functional after the migration.

Troubleshooting Common Symfony Mailer Issues

Here are some common issues users face after migrating to Symfony Mailer:

• Ensure templates are updated to fit Symfony Mailer’s structure, especially for inline styles.
• Furthermore, double-check DSN settings and encryption protocols if experiencing connection issues.
• Also, configure SPF, DKIM, and DMARC records and check content for spam triggers.
• Additionally, email queuing should be implemented to prevent overloads and optimize SMTP server settings.
• Verify correct SMTP transport settings and ensure our mail server allows access from our IP.

[Need assistance with a different issue? Our team is available 24/7.]

Conclusion

Migrating from Swift Mailer to Symfony Mailer is a smooth process when done correctly. By backing up our site, uninstalling conflicting modules, and following the outlined steps, we can successfully migrate to Symfony Mailer while preserving our custom email templates and configurations. With Symfony Mailer’s integrated UI, sending test emails and managing email settings is easier than ever.

In brief, our Support Experts demonstrated how to migrate SwiftMailer to Symfony Mailer in easy steps.