This is copied from another forum. I don't know if it will work with "Incredimail".....sorry, I'd dump Incredimail if I were you. It's junk.
There's a "glitch" in the Netscape.net webmail setup wizard in Netscape 7.xx mail. You have to click "cancel" when you get the "connecting to server" message after you type in your name.
The Netscape.Net Webmail forum here has a number of threads on this issue. For example:
"Mailbox creation on webmail server failed" messag "
Email account setup
Here is the "workaround":
From a Netscape 7.xx MAIL window, go to Edit > Mail&newsgroup Account Settings.
Click on Add Account > Netscape Webmail account > "I have an existing account".
Enter the screenname and password for the new netscape.net account under "Current Member sign-in". The Netscape Mail Setup window should appear, asking for the name you want to appear in the "from" field.
After typing in your name, click the Next button, and wait a few seconds after the "connecting to server" message appears, then click "Cancel".
Then click "Next", then "Finish" and the Netscape Webmail account will be set up in Netscape 7.x Mail.