Laravel dispatch after response appends error to the response - php

Question

In the Laravel documentation there is this part:
You may also dispatch a closure and chain the afterResponse method onto the dispatch helper to execute a closure after the HTTP response has been sent to the browser:
use App\Mail\WelcomeMessage;
use Illuminate\Support\Facades\Mail;
dispatch(function () {
Mail::to('taylor#example.com')->send(new WelcomeMessage);
})->afterResponse();
This works perfectly fine when the mail is successfully sent. However, when there is an error in the mail sending function, for example, if I intentionally misconfigure the mailing service credentials in .env, then Laravel appends a {"message": "Server Error" } to the response.
Here's an excerpt from the actual code:
public function register() {
try {
dispatch(function () use ($user) {
Mail::to($user)->send(new Register($user));
})->afterResponse();
} catch (Exception $e) {
return response()->json(['success' => true]);
}
return response()->json(['success' => true]);
}
When the mail succeeds, the JSON data {success: true} is returned for the ajax call to process. However, when there is an error in the mail sending part, the following message is returned:
{"success":true}{
"message": "Server Error"
}
The try-catch blocks didn't seem to help.
Any ideas why is that message appended to the response data?