Hi there! I understand how frustrating it can be when emails don't go through, especially when you're trying to send attachments. Let's get this sorted out together!

To start, can you tell me if you’re receiving any specific error messages besides the "500 messages unexpected error"? Also, it would be helpful to know if you're using any particular file types for the attachments that are failing to send.

Meanwhile, here are some basic troubleshooting steps we can try:

1. Check Your Internet Connection: Make sure that your device has a stable internet connection. Sometimes, connection issues can prevent emails from being sent.

2. Clear the Cache: Clearing the cache and cookies on your WebKit browser can sometimes resolve unexpected errors. You can do this by going to your browser settings, finding the privacy section, and selecting the option to clear browsing data.

3. Restart Your Computer: A simple restart can sometimes resolve temporary issues with programs or software.

4. Check for File Size Limits: Ensure that the attachments you're trying to send don’t exceed any file size limits set by Criptext. If they're too large, consider compressing them or sending them in smaller parts.

If these steps don't resolve the issue, we could dive deeper into specific settings or account checks. Please let me know what you’ve tried or if there are any additional details you can share!