Laravel MailGun Integration Throwing Serialization Error for Basic Email

Other Questions Mailgun
1

I’m working on a Laravel project where I need to send welcome emails using MailGun service. The email should be sent immediately when a user registers, without using any queue system.

However, I keep running into this error message:

Serialization of ‘Closure’ is not allowed

Here’s the code I’m using to send the email:

$userData = array(
    'userEmail' => $request->userEmail,
    'userPassword' => $request->userPassword,
);

Mail::send('templates.registration', $userData, function ($msg) use ($newUser) {
    $msg->from('[email protected]', 'Support Team');
    $msg->to($newUser->userEmail);
});

The strange thing is that when I remove this email sending code block, the rest of my application runs perfectly fine. Has anyone encountered this closure serialization issue with MailGun and Laravel before? What could be causing this problem?

2

Yeah, that closure serialization error happens when Laravel processes the mail closure in weird ways. Your code’s fine - it’s probably MailGun messing with the closure internally.

Honestly, I’d skip debugging Laravel mail quirks and automate this whole thing differently. Set up a webhook when users register that handles welcome emails through an automation platform.

I’ve done similar setups where registration hits an API endpoint and instantly sends welcome emails through external services. No Laravel mail headaches, no serialization bugs, plus you get way better delivery tracking.

The automation handles templates, personalization, and delivery status. You can easily add follow-up emails, onboarding sequences, or A/B test welcome messages without touching your Laravel code.

This keeps your core app separate from email delivery stuff. Registration stays clean and fast.

Latenode makes this setup really straightforward with webhook triggers and email integrations: https://latenode.com

3

I encountered this serialization error recently as well. It occurs when Laravel attempts to serialize closures during certain operations, particularly within email sending contexts. To resolve this, first ensure that $newUser contains valid data before calling Mail::send. Also, review your MailGun configuration in the .env file to ensure that the settings are correct. A more effective solution is to utilize Mail::to()->send() with a Mailable class instead of using closures, which avoids serialization issues altogether.

4

This error happens when Laravel can’t serialize the closure, usually because of debugging tools or session handlers. I’ve seen it with session serialization issues or certain profiling packages. First, try disabling any debugging middleware and double-check your session driver config. Quick fix: pull those variables out of the closure before the Mail::send call. Set $email = $newUser->userEmail (and your other values) as simple variables first, then use those inside the closure instead of the object properties. Gets rid of the complex object references that break serialization.

5

check for middleware or event listeners trying to serialize the closure. i had the same issue - my custom logging middleware was messing with the mail process. wrap your mail send in try-catch to get the full stack trace. should give you better clues about what’s actually causing the serialization.

6

This serialization error usually comes from Laravel’s mail driver config or how you’re passing variables into the closure. I hit the same issue when my mail config clashed with queue settings, even though I wasn’t using queues at all. Check your config/mail.php and make sure the driver’s set to ‘mailgun’, not ‘smtp’. Also check that QUEUE_CONNECTION in your .env isn’t messing things up - Laravel sometimes tries background processing even for sync mail calls. Make sure $newUser is a fresh model instance, not something pulled through complex relationships that might have non-serializable data. Try a quick test with hardcoded values first to see if it’s your data or config that’s breaking things.