服务器端Mailgun部分邮件无法发送问题排查求助

Hey there, I’ve run into almost exactly this issue before—super frustrating when some emails go through and others vanish without a trace! Let me walk through the fixes and debugging tricks that finally got my password reset emails working:

Common Causes & Fixes #

• Check for encoding or special character issues in your email content
  Local and production environments often have different PHP encoding settings (like mbstring configurations). Password reset emails usually include dynamic tokens with special characters, and if production is mangling that encoding, Guzzle might choke on the multipart request without throwing an obvious error. Try swapping your password reset template for plain, static text first to test if it sends—if it does, you’ll know the issue is with the dynamic content’s encoding. Also, log the full email content right before sending to compare local vs production outputs.

• Verify Mailgun domain/API restrictions you might have missed
  Even with a valid API key, Mailgun might silently block certain emails if they trigger their internal filters. Double-check that the sender address for password reset emails is fully verified in your Mailgun dashboard (no typos, and it’s linked to your sending domain). You can also test sending a password reset email directly via curl using your production API key—if that works, the problem is in your code; if not, reach out to Mailgun support, they might have hidden logs about why those emails are being blocked.

• Debug Guzzle’s network requests (they might be getting stuck)
  Production servers often have firewalls, proxy rules, or SSL certificate issues that don’t exist locally. Enable Guzzle’s debug mode to see exactly what’s happening when it tries to send the request:

  // Add this when initializing your Guzzle client
  $client = new \GuzzleHttp\Client([
      'debug' => fopen('/var/log/guzzle_mailgun_debug.log', 'a'),
      'verify' => '/path/to/cacert.pem' // If your server has SSL cert issues
  ]);
  

  This log will show you if the request is hanging during connection, failing SSL verification, or being blocked entirely. Also, confirm that your production PHP has the curl extension enabled and allow_url_fopen isn’t disabled.

• Double-check hidden logic in your password reset flow
  Sometimes there’s a silent failure upstream of the Mailgun call—like a user being marked as inactive, a token generation error that doesn’t throw an exception, or a conditional that skips the actual send without logging it. Add verbose logs right before and after the Mailgun call:

  error_log("Attempting to send password reset to user: " . $user->id . " with token: " . $token);
  // Your Mailgun send code here
  error_log("Mailgun call executed for user: " . $user->id);
  

  If you see the first log but not the second, you’ll know the code is exiting early before reaching the send step.

Quick Debug Hack #

A fast way to isolate the issue is to mock the Mailgun client and log every parameter that’s being passed to it. Compare these parameters between your local and production environments—even a tiny difference (like a missing reply-to address or a malformed recipient) could be the culprit.

If none of this works, consider upgrading your Mailgun PHP SDK to the latest version—v2.3.0 is pretty old, and there might be compatibility bugs with newer Guzzle versions that are causing silent failures.

内容的提问来源于stack exchange，提问作者PsychoMo