How Is It Possible that from One PC Form's Emails Are Received but from Another PC Not Received?

You've already asked this in two other threads. The answer is the same. If your http referrer is blocked AND your script does not process forms with a blocked referrer, the email will not be sent. The http referrer can be blocked by your browser, your pc firewall, add-ins, corporate firewalls or proxy servers. You need to check your code and see if the script is checking a referrer value. It may be something other than the referrer but that's the most obvious place to start. Create a simple script where you can switch referrer checking on and off so you can see exactly what is happening.

Please do not start more threads. It makes it impossible for others to know what has already been asked and tried and we all end up repeating ourselves.

Does the form rely on the user's available email client or does it use the server? It should use the server because the user may not have an email client configured.