The default mail program is the program that is set by Windows as the program to handle email messages in Windows. When another application wants to send an email, it looks up the default and passes the email to the default program.
When you click the "Email and Log Submission" button in 3DIQ, a new message should populate in your email system of choice. If this doesn't happen, it may be because Windows doesn't have the correct default email program set.
For 3DIQ, this will either be a desktop email program (such as Outlook) or a browser-based email program (such as Gmail).
To ensure you have the default set follow the steps below.
In the search bar on the bottom left of the desktop, type Default App Settings and click it.
Click the Mail option, then select the program you wish to make default. For example, if you want Outlook to open when you click "Email and Log Submission", select Outlook. If you want Gmail to open, select Google Chrome.
Once you've set your default email app, try clicking "Email and Log Submission" in 3DIQ to ensure your default app has been set properly.